P38A ABS and Traction Problems

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Q

quavey

Active Member
Posts
551
Location
Lancaster
Hi Guys, right first of this is for a 2001 4.6 Vogue.

Symptoms: ABS Fault followed by Traction Failure on the dash on startup. Traction fault on turning of the ignition. No ABS or TC light on the dash at ANY time

What I have tried:
Brand new sensor on the left rear (old one didnt look to bad but gave identical fault)

Diagnostics:
I've tried a dealer grade Snap On diagnostic machine on the car which will talk to the ABS computer. It has said "164 Rear Left Sensor (Short to another)". When going into the advanced and live information each wheel sensor is showing a voltage of 2.4v apart from the Rear Left which is reading 0.0.

My thoughts are this is a break in the wire from the ABS computer (where is that?) to the the rear left ABS sensor. Surely its not a simply wire from an output pin somewhere? However I am pretty much exhausted with my knowledge or skill as to where to go from here.
 
Right I've had a google with the fault code number I've got and everything I've found is pointing to ecu failure which is a bit of an Arse but to be fair they are not horrific to buy second hand. My only question is as long as it's the 4 channel job with the part number srd100500 will it just work or will it require further coding to the car?
 
quavey said:
Right I've had a google with the fault code number I've got and everything I've found is pointing to ecu failure which is a bit of an Arse but to be fair they are not horrific to buy second hand. My only question is as long as it's the 4 channel job with the part number srd100500 will it just work or will it require further coding to the car?
Click to expand...

Before he starts buying ECUs i would check the duff sensor for resistance first of all. Should be a resistance through it that changes as metal is moved closely across the sensor tip.
 
Well I've tried a brand new sensor and got the same fault. The sensor I took of was dated 2011 so looks like it's had this issue for a while I wonder if they've done a sensor and just left it as there are no warning lights on dash so it will pass an Mot (technically)
 
connector C505 pin 7 and 8 on ABS ECU - check for continuity in wiring to sensor as well. DO NOT try resistance through pins. ECU's tend to get into a huff when 9v gets put through where its not meant to be!
 
Last edited:
Falk said:
connector C505 pin 7 and 8 on ABS ECU - check for continuity in wiring to sensor as well. DO NOT try resistance through pins. ECU's tend to get into a huff when 9v gets put through where its not meant to be!
Click to expand...

For checking the sensor unplugging it and checking for resistance through it is the only way of testing them, you will not get a continuity reading through the sensor. With meter set at 2K you should get around 920 OHMS which should change as metal is moved across close to sensor tip. No resistance reading and the sensor is open circuit and will never work.
 
Thanks for the pin numbers it gives me something to go at. I have not had the ECU out yet so I suppose its possible that there is a damaged pin or some damp in the harness or anything really. What I did wonder, I have a friend who has my old 4.6 Thor. If I borrowed the ECU from that it would give me an open and shut case. However, if we leave the ignition of and just unplug the ECU, try it in mine and then return it to his car without a key anywhere near the igntion will that cause any faults to show on his car? Not a huge issue as can get hold of the diagnostics kit to clear the fault but I'd rather not have to mess.

I'm assuming the ABS ECU and system is totally dead until there is a key in the ignition, is this the case?
 
quavey said:
Thanks for the pin numbers it gives me something to go at. I have not had the ECU out yet so I suppose its possible that there is a damaged pin or some damp in the harness or anything really. What I did wonder, I have a friend who has my old 4.6 Thor. If I borrowed the ECU from that it would give me an open and shut case. However, if we leave the ignition of and just unplug the ECU, try it in mine and then return it to his car without a key anywhere near the igntion will that cause any faults to show on his car? Not a huge issue as can get hold of the diagnostics kit to clear the fault but I'd rather not have to mess.

I'm assuming the ABS ECU and system is totally dead until there is a key in the ignition, is this the case?
Click to expand...

Unplug the sensor and check with ignition on for voltage across the feed wires. If no voltage look to wires, check continuity to ECU connector. If continuity ECU problem. If voltage check sensor as previously outlined.
 
I've just had the same issue with mine. I bought an aftermarket sensor which cured it for a week then same issue with ABS & TRACTION FAILURE. I then bought a second hand Wabco sensor only to get the faults again. I got 'short to another' on diag. Initially i was led to believe it was the ECU as they are a common failure on the newer ECU's. So, paid out £130 for another ECU (stupid me, but was getting desperate to sort for MOT time)! Bear in mind the early ECU's are cheap but not the later black type you have in yours. Anyway, still got the same failures so bought a new Wabco sensor & all is fixed. I have a fully working ECU (SRD100501) if you want to give it a try but would certainly check the sensor resistance first as already said, If i'd done this properly myself before jumping to conclusions i would have saved myself time & money.
 
martynv8 said:
I've just had the same issue with mine. I bought an aftermarket sensor which cured it for a week then same issue with ABS & TRACTION FAILURE. I then bought a second hand Wabco sensor only to get the faults again. I got 'short to another' on diag. Initially i was led to believe it was the ECU as they are a common failure on the newer ECU's. So, paid out £130 for another ECU (stupid me, but was getting desperate to sort for MOT time)! Bear in mind the early ECU's are cheap but not the later black type you have in yours. Anyway, still got the same failures so bought a new Wabco sensor & all is fixed. I have a fully working ECU (SRD100501) if you want to give it a try but would certainly check the sensor resistance first as already said, If i'd done this properly myself before jumping to conclusions i would have saved myself time & money.
Click to expand...


This is the thing that's leading me towards ECU, I don't actually have any lights on the dash for TC and ABS. I do have the handbrake warning light which stays on until the brake booster pump reaches pressure. I mean that the bulb check does not even work. Ive had a close look at the dash and although I suspected that the bulbs might have been taken out I cant really see how without making a bit of a mess of it. Ive had a chat with dad whos going to help me put a meter across each of the rear sensors and compare and also from the ECU pinouts. Ive found one for £90 plus postage on fleabay. The sensor I took of is a genuine wabco dated 2011, which I have a receipt for in the history. If I'm honest I expect shes had the fault since then but as no warnings on the dash when it comes to MOT it doesn't fail.
 
Strange if there's no check light for ABS & TC. Maybe PO removed bulbs to hide a fault. This should be picked up by an MOT tester though? I'd check whats going on with the bulbs in the dash first. Can you remove the other sensors or are they rusted in? You could always swap around them to see if the fault follows.
 
quavey said:
This is the thing that's leading me towards ECU, I don't actually have any lights on the dash for TC and ABS. I do have the handbrake warning light which stays on until the brake booster pump reaches pressure. I mean that the bulb check does not even work. Ive had a close look at the dash and although I suspected that the bulbs might have been taken out I cant really see how without making a bit of a mess of it. Ive had a chat with dad whos going to help me put a meter across each of the rear sensors and compare and also from the ECU pinouts. Ive found one for £90 plus postage on fleabay. The sensor I took of is a genuine wabco dated 2011, which I have a receipt for in the history. If I'm honest I expect shes had the fault since then but as no warnings on the dash when it comes to MOT it doesn't fail.
Click to expand...

It should do if the lamps don't work. MOT tester is slipping up with that one.
 
This is my worry, of course its last owner had it for however long and if they had a generous MOT tester then fine. I'm not in a position to be sure that it'll ever get through a ticket, despite it being relatively safe its the fact that the ABS doesnt work and its no traction control which is why I'm so bothered about getting it fixed.

Does anyone know if those bulbs are a bulb or an LED in the back of the cluster?
 
Yeah I have seen that to be fair, having re-read it it seems that they are bulbs. I'm assuming that I should really take the battery of before trying to remove the cluster. Will order a few bulbs for it and see if there are some gaps!
 
quavey said:
Yeah I have seen that to be fair, having re-read it it seems that they are bulbs. I'm assuming that I should really take the battery of before trying to remove the cluster. Will order a few bulbs for it and see if there are some gaps!
Click to expand...

Could take it off, easier to just disconnect it ;)
 
martynv8 said:
I've just had the same issue with mine. I bought an aftermarket sensor which cured it for a week then same issue with ABS & TRACTION FAILURE. I then bought a second hand Wabco sensor only to get the faults again. I got 'short to another' on diag. Initially i was led to believe it was the ECU as they are a common failure on the newer ECU's. So, paid out £130 for another ECU (stupid me, but was getting desperate to sort for MOT time)! Bear in mind the early ECU's are cheap but not the later black type you have in yours. Anyway, still got the same failures so bought a new Wabco sensor & all is fixed. I have a fully working ECU (SRD100501) if you want to give it a try but would certainly check the sensor resistance first as already said, If i'd done this properly myself before jumping to conclusions i would have saved myself time & money.
Click to expand...

How cheap is your ECU if I do end up needing one ?! ;)
 
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