M

maxderby

Member
Hi All
my 2001 Diesel 2.5 P38 has the Abs and Traction control lights permanently on, firstly a scan showed nearside front abs sensor fault so replaced both front sensors , this worked very briefly about 2 days then abs and traction light back on, another scan then said 2 valves open in master cylinder, contacted chap I bought it off and he said use nanocom to force them to move, unfortunately I dont have one, I tried bleeding the whole brake system as described in the manual, but no results

Chap I got it off sent me a new master cylinder which is now on and still the same faults, I did notice the big block connector that goes to this unit had the spiraband sheathing peeled back about 7inch, so suspect in past someone has been looking for a fault, after fitting new unit had it scanned again and the info is in the picture although poor, if you can expand it you can read it but will put what it says

101 No traction Valve - (open circuit )
103 Outlet Isolation Valve - (open circuit )
20 Outlet Isolation Valve - (open circuit )

Im assuming an electrical fault, ive switched out the Black relay for another with no results, is there any other relays to check
, if so how do i check them, otherwise can anyone tell me what wires to bell out, Im no sparky but have some knowledge, I cant see any obvious dodgy wiring or connector but very suspect of protective sheathing being peeled back, any help wiring diagrams or instructions welcome and appreciated
cheers
Maxderby
 

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maxderby said:
Hi All
my 2001 Diesel 2.5 P38 has the Abs and Traction control lights permanently on, firstly a scan showed nearside front abs sensor fault so replaced both front sensors , this worked very briefly about 2 days then abs and traction light back on, another scan then said 2 valves open in master cylinder, contacted chap I bought it off and he said use nanocom to force them to move, unfortunately I dont have one, I tried bleeding the whole brake system as described in the manual, but no results

Chap I got it off sent me a new master cylinder which is now on and still the same faults, I did notice the big block connector that goes to this unit had the spiraband sheathing peeled back about 7inch, so suspect in past someone has been looking for a fault, after fitting new unit had it scanned again and the info is in the picture although poor, if you can expand it you can read it but will put what it says

101 No traction Valve - (open circuit )
103 Outlet Isolation Valve - (open circuit )
20 Outlet Isolation Valve - (open circuit )

Im assuming an electrical fault, ive switched out the Black relay for another with no results, is there any other relays to check
, if so how do i check them, otherwise can anyone tell me what wires to bell out, Im no sparky but have some knowledge, I cant see any obvious dodgy wiring or connector but very suspect of protective sheathing being peeled back, any help wiring diagrams or instructions welcome and appreciated
cheers
Maxderby
Click to expand...
The ECU is a known failure item, first check the connector at the ECU for corrosion.
All the wiring diagrams are in RAVE which can be down loaded I think from a link in the tech archive.
 
hi
thank you for your reply, is that the main ecu next to the battery or the one behind the glove box, ive tried my mates ecu from behind the glove box with no difference
cheers
Maxderby
 
maxderby said:
hi
thank you for your reply, is that the main ecu next to the battery or the one behind the glove box, ive tried my mates ecu from behind the glove box with no difference
cheers
Maxderby
Click to expand...
The ECU next to the battery is for the engine. The SRS ECU is the one up behind the glove box.
Did you carefully check the connector for corrosion front and back? Just a little verdigris will cause problems.
Did you follow the full bleed procedure as detailed in RAVE?
How many brake presses between pump runs?
What is the battery voltage? Low volts can cause these sort of problems.
You really need a Nanocom to go with a P38, it will be needed fairly often.
 
Last edited:
Hi
Thanks for your reply, yes I checked the connection block, nice and clean, gently pulled the wires to check nothing loose or obviously snapped, I think it was 4 or 5 pumps between pump runs, where is the traction control ECU located, I thought the wabco one behind the glove box was the abs and TC ECU? The srs one on my last P38 was a yellow box with SRS embossed on it, but that was a 95 model, many thanks
Maxderby
 
maxderby said:
Hi
Thanks for your reply, yes I checked the connection block, nice and clean, gently pulled the wires to check nothing loose or obviously snapped, I think it was 4 or 5 pumps between pump runs, where is the traction control ECU located, I thought the wabco one behind the glove box was the abs and TC ECU? The srs one on my last P38 was a yellow box with SRS embossed on it, but that was a 95 model, many thanks
Maxderby
Click to expand...
SRS is Safety Restraint System, nothing to do with traction control which is controlled by the ABS ECU.
 
Are the abs sensors pushed on properly. The little cage that holds them can degrade and the airgap can get too large.
They should be pushed home until the sensor touches the abs ring on the Cv joint head then while moving it'll set its own air gap. 🤔
 
The later 4 wheel TC unit is behind the glove box. I don't know about the earlier ones.
It's a black square shape
 
Thanks all, the front 2 sensors are new, the cages fitted correctly and sensors pushed down as far as possible, plug in readers show no abs faults, snap on and auto logic, no access to nanocom that everyone seems to get excited by, maybe I need to check rear and abs rings but readers are saying open circuit which normally means electrickery problems hence asking for wiring diagram just to bell relevent wires out unless someone can.tell me which ones to test and where to find them, would the becm be causing problems, many thanks Maxderby
 
Just because the sensors are new, doesn't mean they work. Myself and others on here have first hand experience of that.
If snapon and autologic don't see faults when clearly you have at least one, then dare i suggest they aren't compatible?
Everyone's gets excited about nanocom because it's current and it works on all parts of the car, 100%
 
maxderby said:
Thanks all, the front 2 sensors are new, the cages fitted correctly and sensors pushed down as far as possible, plug in readers show no abs faults, snap on and auto logic, no access to nanocom that everyone seems to get excited by, maybe I need to check rear and abs rings but readers are saying open circuit which normally means electrickery problems hence asking for wiring diagram just to bell relevent wires out unless someone can.tell me which ones to test and where to find them, would the becm be causing problems, many thanks Maxderby
Click to expand...
Open circuit may not mean what you think it means, it may just mean no signal. Unlikely to be BECM related.
 
Hi
I thank you all again, if new ABS sensors can be duff how do you test them before you fit them? Can we clarify where the traction ECU is, its a 2001 model and i thought it was behind the glove box and made by Wabco, I dont know why the SRS was mentioned as I know it doesnt affect the issues I have, is it just the black relay for the ABS or are other relays involved, I still think its in the wiring but willing to check things people suggest, is there anyone in Derby Derbyshire with a Nancom that wants to plug it in for a Drink, Is there also a Auto electrician in same area that would like to have a go, this bit is random I know but can anyone tell me on the EAS valve block what colours on the pipes relate to what corner, serviced the valve block and compressor now every morning the drivers front corner is on the bump stop!! and it sometimes seems to take a while to figure out what to do, meaning the air tank is full you press the button up or down depending where it is and some days it leaps there, then other time it just waits forever the leaps into action, Im suspecting the driver? I know I havent done owt stupid like snag an O ring
Cheers
Maxderby
 
You can test the wheel sensor with multimeter set to ohms. Why they can fail after a short time i don't know, maybe just cheaply made
 
The 4 wheel sensors go direct to the wabco unit with no joins in the loom other than where they actually plug in near the wheel
 
Hi Kermit
thanks, that clears that up as thats what mine looks like, do you know what pins on the ECU relate to the ABS and which corner, I could then at least bell them out and eliminate at least one more possibility
 
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