Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hello.

I have a Cav MK3 1.8i with an ABS fault. The light comes on and goes out as it should then after driving a little bit the light comes on. I checked the flash codes and I get 55 which is apparently an issue with the ECU.

I believe this is the later ABS system where the ECU is attached to the Bosch pump in the engine bay. I've attached a picture for reference.

Is there a way of testing what exactly has failed within in ECU? I am an electronics engineer so I am able to test components like the diodes etc or should I just try and track down another working pump and transplant the ECU (if that's even possible)

Any help would be greatly appreciated. The MOT is in a couple weeks and while it may technically pass because it still initialises it would be good to know if I can fix it properly for saftey sake.

Thanks!

On the ALDL plug, short A and K, count the flashes, read the answer below:

16 LH Front Solenoid ( Relay & Connections )
17 RH Front Solenoid ( Relay & Connections )
18 Rear Solenoids ( Relay & Connections )
19 Solenoids Relay Circuits
25 Faulty Sensor toothed Ring
35 Pump Relay Circuits
37 Stop Lamp Switch ( Pedal Switch )
39 LH Front Speed Sensor ( Air Gap & Operation )
41 LH Front Speed Sensor ( Resistance & Connections )
42 RH Front Speed Sensor ( Air Gap & Operation )
43 RH Front Speed Sensor ( Resistance & Connections )
44 LH Rear Speed Sensor ( Air Gap & Operation )
45 LH Rear Speed Sensor ( Resistance & Connections )
46 RH Rear Speed Sensor ( Air Gap & Operation )
47 RH Rear Speed Sensor ( Resistance & Connections )
48 System Voltage High/Low ( Alternator & Battery )
55 Faulty ECU

vexorg wrote: ↑Fri Jul 22, 2022 6:38 pm On the ALDL plug, short A and K, count the flashes, read the answer below:

16 LH Front Solenoid ( Relay & Connections )
17 RH Front Solenoid ( Relay & Connections )
18 Rear Solenoids ( Relay & Connections )
19 Solenoids Relay Circuits
25 Faulty Sensor toothed Ring
35 Pump Relay Circuits
37 Stop Lamp Switch ( Pedal Switch )
39 LH Front Speed Sensor ( Air Gap & Operation )
41 LH Front Speed Sensor ( Resistance & Connections )
42 RH Front Speed Sensor ( Air Gap & Operation )
43 RH Front Speed Sensor ( Resistance & Connections )
44 LH Rear Speed Sensor ( Air Gap & Operation )
45 LH Rear Speed Sensor ( Resistance & Connections )
46 RH Rear Speed Sensor ( Air Gap & Operation )
47 RH Rear Speed Sensor ( Resistance & Connections )
48 System Voltage High/Low ( Alternator & Battery )
55 Faulty ECU

I have done this already. I get flash code 55

New ecu then

There are several companies that claim to be able to repair "any ECU". Just putting "ECU repair" into Google brings up a number of these, and they might be worth a try.

I looked on TIS for fault code 55.
It does not give any help at all.

Simply saying -
The fault is recognized if there is a defect in the control unit when the ignition is switched on or while travelling.

On fault recognition, the ABS is switched off and the ABS telltale is switched on.

---------------------------

Nothing to lose, so before buying a new module....

What I would do is -
disconnect and clean all connectors, fuses and relays for the ABS module.
Put it all back together and see if a fresh reboot clears the issue.

I cannot see any internal schematics to help at component level.
Just the schematic that you see in Haynes.

Here are all the details I could find.







I hope it helps.

By the way - ignore the wires going off to the right - they are for traction control, which was only really fitted to V6 vehicles as far as I can tell.

The traction control on my Cav V6 stopped working quite a few years back, but the ABS continues to work just fine. Luckily the traction control light only illuminates when it operates, so the lack of traction control has never been an MOT fail issue.
When it did work I found it problematic anyway - you'd be moving slowly up a hill in snowy or icy conditions, and one of the front wheels starts to slip. Immediately, the traction control would cut power to the engine so you'd pretty much stop. It was then MUCH harder to get going again than if you'd just carried on up the hill with some slipping and sliding, carefully controlled.

The electrical part (ecu) just unplugs and unbolts from the ABS, just change it.

Robsey wrote: ↑Sun Jul 24, 2022 6:07 pm Here are all the details I could find.







I hope it helps.

By the way - ignore the wires going off to the right - they are for traction control, which was only really fitted to V6 vehicles as far as I can tell.

Late reply but this helps a great deal! Thanks. I'll post an update if I make any progress

It is only minimally useful.
Not component level - more function level.

Good luck - you have nothing to lose by having a look.
It is faulty anyway.

They are only about £30 for a full abs unit on ebay, just swap the ecu