Thread: D4 2.7 - Booster / Master Replacement - ABS Bleed Problems

Hey all,

Completed a booster and master cylinder change on the D4 the other week. Fairly easy to do but I didn't bleed it properly. Yesterday I did another bleed but also did an ABS bleed trough IIDTool beforehand.

I think I've had a dumb dumb moment and messed up the abs bleed somehow because I'm getting the following:

ABS-Brake Module
U3000-4B - Control module - System internal failure - over temperature (28)
( on 01-08-2023 14:56:22 at 206612 km )

FCDIM-Front Control
B10BD-13 - Multi-functional switch - General electrical failure - circuit open (28)

PBM-Parking Brake
U0415-00 - Invalid data received from ABS control module (28)
( on 01-08-2023 15:09:08 at 206612 km )

PCM-Engine Diesel 2.7L
P0625-11 - Generator field terminal - circuit low - General electrical failure - circuit short to ground (2

Could I have shorted the ABS module somehow by overheating it during the ABS bleed sequence? I could smell faint electrical burning when I started the car after about 15 minutes. I'm assuming if the module is cactus, it's sent the signal along the canbus line?

Thanks for reading.
Jamie

Update on this interesting saga is that the wires were all intact so I replaced the alternator and that fixed all the fault codes for open circuit and multi switch.

I sourced a second hand ABS unit and had it on hand ready to swap over. I plugged this unit in and had a couple of fault codes, these are standard I believe. One is that the ABS serial numbers didn't match and one is for Yaw sensor that was not calibrated. Apparently you can fit another unit without reprogramming it, it will work but throw a serial number fault code. Anyway, plugged my original unit back in and cleared the codes - none returned. Bosch state an ABS ecu reset can be done via power off and power on, this may have cleared the over temp fault internally(?).

It appears that the ABS unit just overheated during the bleed, just like Josh said above. Fingers crossed it stays that way.

For others who may need a new ABS unit you have the following options:

1. brand new unit - virgin unit that will be accepted by the ECU - $$$$
2. second hand unit - reprogram this or install with consistent fault code.
3. send unit for repair - Melbourne ABS repair shop couldn't help with this as the "part number" is different. It is a standard Bosch Series 8 E4 proprietary unit (LR stamped of course) so I'm not sure why they couldn't find it. Or send this off to the UK for assessment and repair I suspect this is the cheapest and best option to retain your original unit and serial.

Regarding the ABS bleed, I learnt the following:

1. there are no shortcuts - follow the technical guides the topix one gives you enough info ...Bosch state the pedal must be actuated continuously during abs bleeding so don't stop.
2. have the battery on supply power. (this cost me an alternator)
3. The bleed sequence is a 2 person job. You need clear access to each calliper and one person pumping and reading the action sequence.
4. You could do it without a pressure bleeder but you'll need a fluid top up after the rears are done.

For me, the IID tool bleed sequence just rolled straight through each wheel without checking for completion, it was very difficult to run around to each wheel.