Engine Service Connector not working - can't set proper ignition timing

This is already a great new site for Toyota Van owners and I greatly appreciate this helpful service for van owners!

My 88 LE 4WD has been an ongoing challenge and a frustrating, yet wonderful, experience. The stumbling block I'm currently trying to overcome is jumping the engine service connector to properly set the ignition timing, as well as receive trouble codes. After many part changes, including a headgasket job, my idle was poor. So, I cleaned out the throttle body and replaced the throttle position sensor (TPS). After properly installing the new TPS, my gas mileage went way down and hesitated at highway speeds. So, I thought since the TPS acts as the spark advance, my timing needs to be reset. My only problem is that when I try to jump the two wired engine service connector, nothing happens...no check engine light. Therefore, I cannot set my base timing. 14 mpg is unacceptable for me.

So, my question is...what can be done? Can I bypass the ESC terminal for setting base timing (12 degrees) by unplugging the TPS (spark advance)? Or, can I just set my timing to advance timing (20 degrees) with TPS plugged in and ESC not working (not jumped)? Or, do I need to address an electrical problem (ESC or ECU)? Any help from the pros would be greatly appreciated!!!

Make sure you have the correct connector jumpered. there are a few in the area. One is a check connector for the fuel pump and can be confused with the timing connector. I know mine doesn't always respond if I jump it when the engine is running so I sometimes have to cycle the ignition switch before it takes.

If that doesn't work you can get pretty close by using the 20* mark at idle assuming the engine is at temp and idle speed is set correctly. I run bigger tires on my 4wd and get an average of 16-17 mpg on a new engine.

About unplugging the tps: dont. The ecm has to see the idl circuit of the tps closed to give you proper timing whether the check connector is jumpered or not. if the idl circuit is not closed you will never get your timing right. your symptoms sound like your timing is a little slow. did you adjust the tps angle with a volt meter when you installed it? This would still not explain not going into timing set mode. If you are sure your tps is functioning properly and still can't get it try the 20* method.

Hello Bala. 1st thing we need to do is make sure you are jumping the correct connector. On your van the "Check Engine Connector" is among a group of 3 dead-end terminals right behind the air flow meter. It's the medium sized one and the only one with 2 wires going to it. One wire is brown and the other is gray with a black stripe. Here are some pictures of the "check engine connector":

http://i8.photobucket.com/albums/a23...v/IMG_0104.jpg

http://i8.photobucket.com/albums/a23...v/IMG_0106.jpg

http://i8.photobucket.com/albums/a23...v/IMG_0107.jpg


If nothing happens when you jump those wires (no check engine light and no change in idle), and the connector is in good shape, then this indicates a problem with the ECU or the Check Engine circuit somewhere in the harness. You could try swapping ECUs (if you happen to have an extra one laying around) or you could test the harness with an ohm meter at the ECU connectors. Since you probably don't have an extra ECU, then you'll need to gain access to your ECU (mounted in the D/S pillar behind where your seat belt retracts to), and unplug the harness. Now you can test for continuity between positions "T" and "E1" in the harness. Here is a map of the ECU connections:

http://i8.photobucket.com/albums/a23...v/IMG_0116.jpg


http://i8.photobucket.com/albums/a23...v/IMG_0118.jpg

With the "check engine connector" empty there should be no continuity. With it jumped there should be. If the harness tests okay, then the problem is in your ECU. If you are not getting continuity between these 2 pins with the jumper in, then your problem is in the harness. If this is the case, your choice would be to find the fault and repair the harness or you could cut some insulation off these two wires at the ECU and touch them together. Touching them together at the ECU will have the same effect as jumping the engine connector, but would be somewhat of a "hack" thing to do. If you go this route, just be sure to tape them up when you're done.

If none of this works, tell me what you did, what you found, and we'll move on to a couple other things you can try. Tim

PS: When you changed the TPS did you adjust it per specs using an ohm meter?

while we wait for a response to this post; Tim, is that your toyota parts department in the background? It appears very well stocked.

tim; what amount of money would you say is currently invested on your " stock" :wave2::wnk:

Yeah, that's part of it. I don't know how much $$$ I have invested, I just stock the things I need the most and / or I'm afraid will become NLA. Tim

I'm definitely jumping (or trying to jump) the right connector. My new TPS was also installed and adjusted correctly (with the throttle body off) according to Tim's instructions on another forum, and according to the book. Maybe it went out of spec while re-installing the throttle body. I will check the TPS, the ECU, and the harness this weekend. The TPS would have no bearing on me being able to jump the ESC, but is essential to have adjusted right for establishing proper ignition timing. I think my previous timing was set with a faulty TPS. I had severe idle problems. Once I swapped out the bad TPS for a new one, the idle problems went away, but so did my 19-21 mpg. Because I couldn't previously jump the the ESC, I just set the timing at 12 degrees. This must mean my timing is "retarded" since I set it at 12 degrees with the spark advance (TPS) activated.

It may be a stupid question but are you sure your check engine lamp is working? does it come on during bulb test when you first turn the key? Just trying to cover all the bases.

If you are going to be doing much driving in the mean time I would suggest you bump the timing up to around 20* without the check connector jumped. Slow timing makes engines run hotter, burn oil, pistons, and rings among other things. In other words, it isn't good.

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Originally Posted by NEC

It may be a stupid question but are you sure your check engine lamp is working? does it come on during bulb test when you first turn the key? Just trying to cover all the bases.

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When I turn the key so that the battery comes on, all dashlights except the fuel and check engine light come on. Are they supposed to come on? When I first got my van the check engine light was on until I replace the O2 sensor. I've driven the fuel tank down so low that the fuel light has come on before...so they have worked in the past.

Yes, your check engine light should be on when you turn on the ignition and engage the battery; it should not remain on or come on when the engine is running.

I would recommend visiting skyflyer9's excellent post on dash removal, pull the cluster, and replace the bulb for the CEL.

Gwen

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Originally Posted by timsrv

With the "check engine connector" empty there should be no continuity. With it jumped there should be. If the harness tests okay, then the problem is in your ECU. If you are not getting continuity between these 2 pins with the jumper in, then your problem is in the harness. If this is the case, your choice would be to find the fault and repair the harness or you could cut some insulation off these two wires at the ECU and touch them together. Touching them together at the ECU will have the same effect as jumping the engine connector, but would be somewhat of a "hack" thing to do. If you go this route, just be sure to tape them up when you're done.

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I removed the seatbelt mounting and unplugged the two harnesses that contain the two pins as shown in the picture. With a paper clip in the service connector, the harness showed continuity of + or - 4. Same as when I put the paper clip on the two terminals in the harness and checked continuity at the ESC. When I plugged the harness back into the ECU I did not get continuity at the ESC. Does this mean I need to start looking for a new ECU? Can I risk hunting one down at the U-Pull? I can't believe this would be the only problem with my ECU?

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Originally Posted by llamavan

Yes, your check engine light should be on when you turn on the ignition and engage the battery; it should not remain on or come on when the engine is running.

I would recommend visiting skyflyer9's excellent post on dash removal, pull the cluster, and replace the bulb for the CEL.

Gwen

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Are the bulbs Toyota parts only or can I get them at any auto part store? I can't imagine them being Toyota only, but nothing seems to surprise me anymore when it comes to finding/accessing parts to these vans.

I highly doubt they're proprietary. I have to admit I pull them out of parts vans just because they're on the other side of the yard (quick) and the nearest auto parts store is a hefty drive into town (NOT quick).

I looked it up in the various manuals and none of them list the specs for the bulbs. However, since I know we can get LED dash light replacements aftermarket, I strongly suspect that not only would any decent auto parts store have the bulbs for the warning lights, but they could tell you what you need as well.

Gwen

Quote:

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Originally Posted by NEC

It may be a stupid question but are you sure your check engine lamp is working? does it come on during bulb test when you first turn the key? Just trying to cover all the bases.

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Even if the bulb did not work, it would have no bearing on adjusting the timing. When I set the timing I was attempting to jump/trip the ESC to set base ignition timing. When I removed the trip from the ESC the timing would not jump to 20 degrees.

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Originally Posted by Bala

When I turn the key so that the battery comes on, all dashlights except the fuel and check engine light come on. Are they supposed to come on? When I first got my van the check engine light was on until I replace the O2 sensor. I've driven the fuel tank down so low that the fuel light has come on before...so they have worked in the past.

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If you turn the key two clicks (to ON but not to START), the Check Engine Light should definitely come on, along with the Charge Light and a few others.

It's entirely possible that the bulb is burned out (and these bulbs ARE available at your local big-box auto parts store)...it's not hard to remove the instrument cover panel and the combination meter, and if you do, you could always switch a known working bulb (behind one of the panel indicators that does light up) with the Check Engine bulb, just to rule that part out of the equation. The bulbs are in twist and pull sockets, and they are interchangeable. Just by visual inspection, you'll probably be able to tell if the CEL is burned out.

You are correct that a burned out bulb wouldn't have an effect on your timing adjustment vis-a-vis jumping the check engine connector, however if it is a burned out bulb you can't read any trouble codes the ECU is throwing.

If there are trouble codes stored, I'm not sure that would inhibit you from correctly setting the timing, but you may have more than one problem happening at once, which is common. The electrical systems on these vans are quite sensitive (just like the cooling system) and it doesn't take much to throw two or three things out of whack...

(I have a migrating electrical problem with my '87, so I definitely feel your pain...as I troubleshoot one circuit and move on to the next, the problem seems to jump circuits...ghosts in the machine...there is a simple answer to both our problems, we just need to find out what it is...:dizzy:)

Quote:

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Originally Posted by NEC

It may be a stupid question but are you sure your check engine lamp is working? does it come on during bulb test when you first turn the key? Just trying to cover all the bases.

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:doh:. Okay, yes, I should have thought of that. You should get the Check Engine Light when the key is in the run position (with the engine not running). If you don't have that, then you need to pull your cluster off and check the bulb. The bulb is a #158 and should be readily available at any number of auto parts stores. If your TPS is not adjusted properly, the electronic advance won't necessarily change when you jump / unjump the Check Engine Connector, so it's very possible you have multiple problems with a burned out Check Engine bulb being one of them :doh:. If changing the bulb gets the Check Engine Light to blink when the Check Engine Connector is jumped, but the timing still doesn't advance when you pull the jumper, then move on to the TPS and verify it's set up and working correctly. Tim

Quote:

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Originally Posted by NEC

It may be a stupid question but are you sure your check engine lamp is working? does it come on during bulb test when you first turn the key? Just trying to cover all the bases.

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Holy smokes! After testing out my ECU and harness, re-adjusting my TPS, and taking my dash apart, I realized that the last hired "hack job" mechanic took out my check engine light. I mean, it wasn't even in there...gone....I feel so dumb and cheated. I put a new bulb in there and the engine service connector, or check engine connector, works! I was able to set my base timing and advanced timing.

However, I'm getting a code 51 which could be TPS or AC. I yanked my AC out months ago but left all potential wiring and sensors. Could that be what's setting off code 51? Or, could I still not be properly adjusting the TPS? This could start off an entirely new thread about properly installing/adjusting the TPS...

Ha ha! That's a heck of a thing to find. What some "mechanics" will do to fix a "check engine" light issue :no:. Glad you got it figured out. You are correct about code 51. It could be an issue with an AC sensor or your TPS. Make sure the AC and all accessories are off when you check codes. If you still get the same thing then I would reset the codes, run the van for a few days and re-check. If that code stays gone then you're good. If it comes back, then recheck your TPS. BTW, you can check your TPS the same way you checked the Check Engine Connector (by accessing wires at the ECU). I prefer to check them this way (rather than removing the throttle body or by piercing wires). Tim

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Originally Posted by timsrv

Ha ha! That's a heck of a thing to find. What some "mechanics" will do to fix a "check engine" light issue :no:. Glad you got it figured out. You are correct about code 51. It could be an issue with an AC sensor or your TPS. Make sure the AC and all accessories are off when you check codes. If you still get the same thing then I would reset the codes, run the van for a few days and re-check. If that code stays gone then you're good. If it comes back, then recheck your TPS. BTW, you can check your TPS the same way you checked the Check Engine Connector (by accessing wires at the ECU). I prefer to check them this way (rather than removing the throttle body or by piercing wires). Tim

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Yeah...I'm still shaking my head. Since I removed my AC unit, is there anything remaining that could generate code 51? I removed the AC belt wheel, but my AC idle up and wiring all remain.

As for the TPS...my TPS is only two months old. Can't the TPS be adjusted/tested while attached to the throttle body, with the throttle body attached? I just remove the air intake hose and the TPS connector, place the feeler gauge between the butterfly and throttle stop screw, and test terminals IDL and E1 with a multimeter (ohm setting). :cnfsd:

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Originally Posted by Bala

I removed the AC belt wheel, but my AC idle up and wiring all remain.

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I wish I could shed more light on the rest of this, but I can tell you my A/C idle up, VSVs and wiring remain, and I do not get a CEL.

Gwen

Quote:

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Originally Posted by llamavan

I wish I could shed more light on the rest of this, but I can tell you my A/C idle up, VSVs and wiring remain, and I do not get a CEL.

Gwen

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Thanks for the input. It must mean that my TPS is just not accurately dialed in. :doh: Is the throttle stop screw supposed to be set at closed throttle position? I can't find much info on this. Or is the stop screw supposed to be a little further advanced (not fully closed)?

Okay, well here's an easy way to check for correct adjustment of your TPS.

Take your D/S seat belt reel off and unplug the ECU. Now take a couple of paper clips and put them in terminals marked IDL & E1 below:

http://i8.photobucket.com/albums/a23...G_0116-1-1.jpg

http://i8.photobucket.com/albums/a23...G_0118-1-1.jpg

Now take your multimeter, set it to emit a tone when continuity is detected and hook it up to the paper clips (it should start emitting a tone):

http://i8.photobucket.com/albums/a23...v/IMG_0120.jpg

Now take a .57mm feeler gauge (.022") and place it in between the throttle stop and the adjuster screw:

http://i8.photobucket.com/albums/a23...s/IMG_0133.jpg

After inserting the feeler gauge, the multimeter should still be emitting the tone. Now remove the feeler gauge and insert a .85mm (.034") feeler gauge into the same spot (you may need to stack 2 or more gauges together to obtain this thickness). If the tone stops with the larger feeler gauge(s) inserted, then your TPS is adjusted correctly and no further action is needed. If you get any different results, then your TPS is out of adjustment (or it's no good). Since yours is new, if there's a problem, it will most likely be an adjustment issue. To adjust, remove the throttle body, take a .71mm (.028") feeler gauge and put it between the throttle and the stop (as pictured above). Now loosen the mounting/adjustment screws of your TPS and slowly rotate the plastic body of the TPS until you find the spot where the tone on your multimeter is on the threshold of going on/off. Once you have found that spot, tighten the adjustment screws and re-check your TPS per the procedure above. While the throttle body is off, clean it out good with throttle body cleaner and compressed air. Use a new throttle body gasket Toyota part #22271-73011 when you put it back on. Also check the condition of the 8mm (5/16") coolant lines in this area and replace them too if they need it.

Note: To anybody with a used TPS, my advice is to not waste time with one if you don't know it's history. Bad TPS's are very very common so when in doubt just replace it. There are detailed tests outlined in the manual, and more often than not a used TPS will fail at least one of these tests.

CLICK HERE for more information on cleaning throttle body and replacing/adjusting TPS.

Tim, thanks a million! The book is confusing and calls for feeler gauge sizes that I can't even find. How do I make sure my throttle stop screw is properly adjusted? Doesn't that need to be proper before adjusting the TPS?

As a general rule you should never need to adjust the stop screw. Toyota sets them to stop the throttle about .095" away from the housing. If it's significantly different than that, then you should put it back to about .095", then start over with testing the TPS. If the TPS tests good, perhaps you can find the original spot of the stop screw by using the TPS adjustment procedure. If you change the stop screw position, and you cannot dial in the TPS, then you will need to pull the throttle body back off and set things up from scratch. Use the idle set screw under the rubber flap to re-adjust the idle speed. Tim

This site rules Tim! I thank everyone of you dedicated van owners. Engine Service Connecter actually works (when there's a light bulb in the dash that a hack job mechanic didn't take out), TPS dialed in to the T, ignition timing set...my van is cruisin! No trouble codes, no worries... Was wondering though...what with the AC would ignite code #51?

Glad to hear you successfully solved your problems! I'm not sure why you'd get a code from an AC issue, but I know there are 3 inputs to the ECU from the AC system: the AC idle-up VSV, the AC magnetic clutch, and the AC cut relay (all of these talk to the ECU). Since the AC switch and the AC amplifier are also tied into these components, a short or malfunction in one of these could possibly throw a code??? I think this is why the FSM says to turn off AC and all accessories before jumping the Check Engine Connector. I'm merely speculating because I've never traced a code 51 back to an AC component. Although it may be possible for one of these things to throw a code 51, in my experience it's never happened (at least not to me). Every time I've seen this code it's always ended up being a TPS issue (no idle signal from the TPS). Tim

I'm not getting any error codes coming up. Can you fill me in on how to check the ECU for stored error codes?

https://www.toyotavantech.com/forum/...vice-Connector

I thought it kept some kind of record of the history of error codes. I guess it just keeps the latest? To reset everything you just turn the key to the off position then it gets reset?

The ECU stores codes until the battery get's disconnected or the EFI fuse gets pulled out. Doing either for 30 seconds or so will clear the codes. Clearing codes should be done each time a problem is repaired. If you don't clear codes they will remain stored in the ECU. This can be confusing the next time you check codes as there could be multiple codes built up from previous problems that no longer exist. Tim

Hello,

I have never changed my TPS and have had my automatic 4WD Van from 90k miles to now 207k miles. It is shifting rough when cold, revving a lot before kicking into gear when trying to reverse and then spinning out a bit. Once it gets to running temp it seems to handle a little better. Does this sound like the symptoms of a failing TPS? I did a tune up 2 years ago, new muffler 2 years ago, replaced O2 sensor 3 years ago, and exhaust is still a little stinky but not smokey. Trying to get a confident diagnosis before I start replacing parts.

Thanks for the help!

Peter

What (if any) codes are you displaying?

There is no check engine light on, could it still be sending a code?

Yes. For more information, click on the link in post #29 of this thread (above). Tim

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Originally Posted by timsrv

What (if any) codes are you displaying?

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Got codes 22 and 51. Am I still looking at TPS replacement or maybe something else?

Thanks Tim!

With those codes we must be talking about an 88 - 89 van......right? Code 22 is an ECU Temp Sensor code, but if that sensor is bad the van will run REALLY bad, so I'm guessing that's an old code that wasn't cleared. Code #51 is almost always a bad TPS. I would recommend clearing codes, driving the van around for a day or so, then check codes again. If code 51 comes back I'd replace the TPS. Based on my experience with these vans, if the TPS has more than 100k miles on it or if it has an unknown history, I'd probably just go ahead and replace it. Keep in mind there's an adjustment procedure, so familiarize yourself with that before you do the job. I posted a video of how that's done at the end of the 1st post in THIS THREAD. Tim

Hi Tim,

Replaced the TMS, got it properly adjusted by following your video (had to use a VPN to view it on YouTube, not throwing codes anymore, but still having the same issue of rough shifting when it isn't warmed up yet. Most obvious example is having to rev the engine in reverse and not feeling it engage in gear until I hit higher rpms, so it spins burns out a tiny bit. Could this be as simple as an overdo transmission fluid change? Anything else I should be investigating? Is there a torque converter that receives fluid from the transmission?

Thanks for your generous time and wisdom!

Peter

Have you checked transmission fluid level? Not shifting into gear @ low RPM while cold is the classic indicator you're running low on ATF. Tim

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Originally Posted by timsrv

Have you checked transmission fluid level? Not shifting into gear @ low RPM while cold is the classic indicator you're running low on ATF. Tim

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Unless I misread the dipstick the level looked a little over max actually.