Previa SRS Airbag Error Code 54

[farmteam]

SRS airbag light came on 8 months ago. Shop read SRS Code 54 - Central Squib: 'could be central module to both driver and passenger airbags or either airbag individually'.

Also happened a few years ago and mechanic solved by correcting the driver seatbelt connector - even though there was no seatbelt light on at the time. Unfortunately, the owner mechanic who fixed it previously was on vacation and the employee mechanic didn't know anything about the prior driver seatbelt connector fix.

Checked all interior SRS connectors AND the driver seatbelt connector (disconnected and reconnected with application of dielectric grease to female heads)
Driver seatbelt connector (not even sure this functions within the SRS?)
Steering wheel connector (driver side of clockspring)
Steering wheel connector (steering column side of clockspring)
Steering column connector (below lower dash panel)
*Confirmed clockspring circuit before reconnecting this
Central Control Unit connector
Passenger airbag connector
No signs of damaged yellow cable housings or plugs

I used the TC / AB ground sequence below driver seat to clear the SRS airbag light - it goes away briefly (few seconds) before coming back. Read on ToyotaNation Previa forum the SRS code must be cleared by OBD2. My OBD2 only has Engine module available - there are no codes present and clearing 'nonexistant' codes doesn't resolve SRS airbag light.

Tried to check the connectors on the Left & Right SRS crash sensors but could not determine how to disconnect them. How do these work?

Any advice on SRS code 54? Do I need to visit dealership to re-set this SRS airbag light code - or determine if the Driver / Central / Passenger SRS units are bad.

How did my mechanic a few years ago make the SRS light go away by correcting the connection in the driver seatbelt? I would ask him but he retired and closed Bolder Auto end of 2019.

[farmteam]

1994 Factory Service Manual arrived today (Ebay). Ran SRS system check (5 cycles ignition ON / OFF 20 seconds each) and pulled error codes (TC / AB ground) as Code 31 (Center Airbag Sensor Assembly Malfunction) and Code 54 (Open in P Squib Circuit). FSM states to resolve Code 54 and then re-test to see if still Code 31 error. FSM has several steps to check connectors/wires to pinpoint the Code 54 error.

Fun with the multimeter is in my near future - wish I had left it all disconnected after checking all of the connectors yesterday. At least I know how everything comes apart this time.

[farmteam]

FSM process for Code 54 was pretty simple. Turns out my Central Airbag Sensor Assembly is malfunctioning. Toyota #89170-0W010 looks to be replaced by 89170-28030 from my initial internet parts search.

[farmteam]

Oh Crap!! There are several different 89170-XXXXX Center Airbag Sensor Assembly 'vintages'. I removed malfunctioning 89170-0W010 which is discontinued.

Part # options from the MegaZip.com website - does anyone know if these are interchangable for the Previa SRS system 94-97?

89170-0W010 (01/94-08/95) - replacement 89170-28030 (01/94-08/95)

89170-28030 (08/93-08/95) - not sure why there is a different listing for the same -28030

89170-28060 (08/95-08/96)

89170-28070 (08/96-04/97) - replacement 89170-28071 (08/96-04/97)

I remain hopeful these are interchangable to my 1994 SC's 89170-0W010 malfunctioning original unit.

[farmteam]

Decided to ship my Center SRS Unit to AirbagSystems.com to see if it can be repaired before I attempt purchase / install a unit that may not be fully compatible with my SRS components - stay tuned.

[Previologist]

staying tuned

[farmteam]

Cost me $50 plus $12 shipping and my SRS Center Module returned from AirBagSystems. I have no idea what they did to it - just received an email that it was ready to ship back and to send e-payment. I sent an email asking what they did but haven't received a reply as yet. I do see that someone wrote "Ok" and "45846" with a sharpie.

Unfortunately, I still get the SRS light and it will not clear using the TC / AB ground sequence. We drove without the SRS Center Module last week. I believe I read on another thread that this would require the dealership to clear out the error code?

Also having issues with my instrument panel after installing LEDs. The battery & low fuel lights are always on even though I have a full tank and the battery is charging just fine - including driving 30 miles at night using lights with A/C and radio on - the battery is doing great. Somehow I grounded these bulb circuits in the instrument cluster.

Switched the polarity on the SRS LED bulb to get it to operate after reinstalling the SRS center module - I installed the new LED's while the SRS center unit was out of the van. The SRS LED bulb glows slightly even with the ignition off and the key removed. Strange? Pulled the SRS LED socket out of the cluster until I can determine what I did to mess up the instrument panel indicator lighting.IMG_20200725_135311805.jpgIMG_20200725_135327885.jpg

[farmteam]

I spoke with AirBagSystems on Monday morning before heading out for a family camping trip. Their repair notes state they discovered some minor 'burning' on the circuit board and they replaced 2 components. However, they believe this was a minor issue. Apparently, older SRS units have a pre-set 'cycles' value set by the mfg - when the unit powers-up and verifies the SRS components, it counts as a 'cycle'. When the unit hits the OEM's pre-determined 'cycles' value, the unit creates an error code to the system automatically. The 'cycles' limit is hard wired into the center control module and cannot be re-set.

Not certain but this seems like a pre-determined obsolecense to replace components before their electronic failure. Unfortunately, the OEM's no longer make SRS center modules for a 1994 Toyota Previa. I can replace with a used SRS Center Module, but I have no idea how soon the used installation will reach the 'cycles' limit.

Confirmed that our older SRS system is not 'smart' to know if anyone is sitting in the driver seat - our SRS airbag lights have NOTHING to do with the seat belt sensor connector under the driver seat.

I will now install a used SRS Center module (94-96 vintages are interchangeable by different mfg) to see if my SRS airbag light goes away.

AirBagSystems was very quick to return our SRS Center module and super friendly discussing my unit after their review / repair.