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

[Bala]

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!!!

[NEC]

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.

[timsrv]

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":








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:






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?

[NEC]

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

[jmoa]

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

[timsrv]

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

[Bala]

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.

[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.

[NEC]

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.

[Bala]

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.

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.

[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

[Bala]

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.

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?

[Bala]

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

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.

[llamavan]

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

[Bala]

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.

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.

[skyflyer9]

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.

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...)

[timsrv]

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.

. 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 . 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

[Bala]

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.

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...

[timsrv]

Ha ha! That's a heck of a thing to find. What some "mechanics" will do to fix a "check engine" light issue . 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

[Bala]

Ha ha! That's a heck of a thing to find. What some "mechanics" will do to fix a "check engine" light issue . 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

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).