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ABS / Traction Control lights on after brake job, fluid flush


NickR23

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I have a 2002 p38 (4.6 HSE).  A couple of days ago, I took the car in to replace all brake pads and rotors.  They recommended a BG brake flush etc so i said ok.  It went in with zero idiot lights illuminated.  When I picked the car up they said the the ABS light and Traction control lights are illuminated, (and they still are).  I get the ABS and Traction faults in the message center. 

I left instead of continuing to argue about the reason b/c it was Friday at 1700 and I was late to happy hour etc..  Has anyone ever experienced this issue?  I think it has something to do with the brake flush. 

Yes the car is 15 years old, yes the 3 lights (abs, brake tc) come on very briefly and then off when I would initiate a sudden hard stop.  But did a part fail coincidentally when i had this work performed??  Seems like baloney to me.   Any information would be greatly appreciated. 

Edited by NickR23
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The three lights coming on briefly when you brake hard (and trigger the ABS) is normal operation, as is the TC light coming on if you pull off harshly on a loose surface and trigger that.

I'm not sure what the garage did to trigger the fault, but they did something (possibly starting the car up with no brake fluid in it?). Maybe broke a wire or pulled a connector off?

I'm fairly certain that the ABS system on the P38 will only light up like that when it's currently detecting a fault - if the fault is gone it will store the fault code but just flash when you turn the ignition on (once, I think) to show it has fault code(s) stored.

You can interrogate the ABS controller without any special equipment (unless you consider a paper clip special...) and it should tell you what it's unhappy with - I'll see if I can dig out the instructions.

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Right - single flash mean no fault codes stored, I got that bit wrong. Not sure what you'll get if there is a fault stored (maybe continuous as  you're seeing).

To check the fault codes your ABS controller has stored:

First, turn off the ignition.

Pull the ABS warning relay - small square box with a green base, which you'll find behind the side panel of the left hand front seat base.

Find the ABS test connector (normally used to connect the dealer's diagnostic computer) - it's blue and on the P38 I think it'll be under the front of the right hand seat.

Make sure you have something to write on, then turn on the ignition and use a straightened paper clip or similar to connect the diagnostic connector pin attached to the black wire to the pin attached to the black and pink wire. Watch the ABS light on the dashboard. You should see the following:

  1. A long and then short flash - this indicates that you've entered diagnostic mode.
  2. A sequence of flashes indicating a fault code will then follow - each is indicated by 2.5s flashes of the ABS light in the following pattern: flash, flash, pause, flash, flash, flash (that'd be fault code 2-3). The code repeats, so don't worry if you don't get it first time.

You can clear a fault code by removing your paperclip while that code is flashing (not when the code has finished). Restart the diagnostics and repeat until you've cleared all fault codes (if you have multiple fault codes stored, it will show the first (most recent?) clear that and it will show the next and so on).

You could have old faults stored in the system, or things the garage triggered that they've already sorted, so it's generally best to start by clearing all the fault codes, then go for a drive and check the codes again - that way you should only be looking at current faults.

The fault codes are as follows - can't remember where I copied these from, but they're originally from the workshop manual:

2-6: Stop light switch - faulty switch or wiring. Replace brake light switch.

2-7: Continuous supply to the ECU with the ignition off. Faulty valve relay or wiring.

2-8: No voltage to ABS Solenoid valves. Faulty valve relay or wiring.

Sensor Air Gap
2-12 Front Right
2-13 Rear Left
2-14 Front left
2-15 Rear Right
Reason: Too large an air gap, or sensor has been forced out by exciter ring – try tapping sensor back into place.

3-0 to 3-9: Open circuit or connection from ECU to solenoid valve in booster, or in ECU.

4-0 to 4-9: Short circuit to earth from ECU to solenoid valve in booster.

Sensor Resistance Too High
4-12 Front right
4- 13 rear left
4- 14 front left
4- 15 rear right
Reason: Wiring to sensor is broken or sensor resistance is too high. Inspect wiring at sensors.

5-0 to 5-9: Short circuit to 12 volts in connection from ECU to solenoid valve in booster. Possible earth fault.

Intermittent Connection to Sensor
5-12 front right
5-13 rear left
5-14 front left
5-15 Rear Right
Reason: Sensor wire has an intermittent fault - check connection(s).

6-0 to 6-9: Short circuit between two connections from ECU to to solenoid valve in booster.

No Output From Sensor
6-12 front right
6-13 rear left
6-14 front left
6-15 rear right
Reason: no output from sensor. Sensor may have too large an air gap. Try tapping in sensor(s), check connections.

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If you get the bleeding sequence wrong on an ABS system, you get trapped air.  That is possibility number one.  The second high probability mistake is switching on the ignition with any part of the system disconnected or unbled; it will register a fault and could be triggering the lights even though the work was subsequently completed, needing an ECU fault reset from a diagnostics machine.  The final likely candidate is that they disturbed the sensors during the work and the gaps need resetting.  It seems unlikely that they would have damaged anything during the work, though not impossible, especially if they introduced any dirt from bad fluid or dirty bleeding equipment.

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