Smouser
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- Amesbury, Wiltshire, UK
I posted about my Ford Ranger's ABS issue in the 'Today I fixed' thread a few days ago.
Unfortunately, the ABS issue remains
There will now have to be an extended thread, to save time, I have copied my original post.
The followup will be posted shortly.
Unfortunately, the ABS issue remains
There will now have to be an extended thread, to save time, I have copied my original post.
Problem
The ABS light on my Ford Ranger has been coming on intermittently. I have changed a few sensors before during the life of the truck as the Rangers seem to eat sensors somehow.
It is really annoying when the ABS malfunction light comes on because: not only do you not have ABS, you don't have hill start /hill decent assist, the Electronic Stability Control (ESC) does not work, and finally, the parking sensors don't work either
I don't know what the ABS has to do with the parking sensors, but when the ABS light comes on, it also disables the parking sensors
Symptom
ABS light would come on but then normally it would 'fix itself' in a few minutes while driving. At first, it happened rarely but has been becoming more common over the last two weeks where the ABS light would come on, on every journey.
The main fault code was 'Code: C003A'.
There were other codes too, but they all relate to the rear right wheel speed sensor not working correctly.
Normally, when previous sensors have gone bad, I get an error something along the lines of 'invalid data received from X sensor', this time I got 'Circuit Short or Open'.
On Sunday, the ABS light came on once again, but it did not fix itself. After resetting the code with Forscan, it came back on without me driving/moving the vehicle. At last, the problem was present while parked on the drive. It was time to try and figure out what the problem was.
Diagnoses
Because the sensor was fairly new, I did not expect the problem to be the sensor. The sensor checked out when measured with a multimeter. Besides, it 'fixed' itself regularly and my suspicion was a broken wire/continuity problem somewhere.
My plan was to check for continuity from the rear of the vehicle where the sensor plugs into the harness to the front of the vehicle where the connector connects to the ABS module.
I found the pin layout for the front connector and identified pin 17 and pin 29 to be the right rear wheel sensor.
I simply bridged the two pins with a piece of fire and then used my multimeter to check for continuity at the rear right speed sensor's connector.
Nothing. Open circuit.
At least I identified the problem I thought.
Just to make sure I was doing everything correctly and had the correct pin layout for my vehicle, I checked continuity from the left rear wheel sensor to the front ABS connector and that all worked.
The ABS wiring diagram is pretty simple on paper.
The rear right speed sensor plugs into connector CA426. The cable then goes to connector C3047B and then to C210 and finally, it terminates at C136 (the connector going into the ABS module).
The plan now was to establish where the continuity problem lay in the three pieces of wire/cable/harness.
The first problem was to identify where these connectors were and then to get access to them.
Luckily, I found the wiring diagram for those too.
Connector C3047B is on the left-hand side of the vehicle behind the mudguards. While it is probably possible to get access to it with the wheel on, it would be difficult so I took the wheel off.
I checked the continuity between connector C426 and C3047B - all good.
I then checked the continuity between connector C3047B to C136. Nothing.
It was time to find connector C210 to check continuity from there to the front and also to the rear.
I came across a diagram that indicated connector C210 is on the left-hand side of the vehicle by the passenger footwell. However, I could not find it.
Later, I found a diagram that indicated it was on the right-hand side of the vehicle by the driver's footwell.
I checked the continuity between C210 and C136. All good.
I then checked the continuity between C3047B and C210 but could not get it.
It was late and dark and I had to use the vehicle the next day so I got everything back together.
Today I had some time to continue to try and find the problem. However, now I had continuity from the rear of the vehicle all the way to the front
I hooked up Forscan to monitor the wheel speed sensor outputs.
This is what I found.
The pink line is the rear right and as you can see the line is not smooth like the others. It has got some weird drops.
Maybe the sensor was bad after all (pretty bad going for less than a year old).
I had a spare left rear wheel sensor but the cable on the left rear sensor is a little too short to fit on the right-hand side.
A quick extension of the cable and I fitted it to the rear right.
This is what I got.
Much better and no more ABS light!!!!!
It is working!
For now.......
I have done about 30 miles since I changed the sensor and all is good for now. I still don't know what was up with the continuity problem, maybe there is a damaged wire somewhere and it is back to its working position now or there was a poor connection at connector C210. I just don't know
I hope I don't have to post in the 'Today I broke' thread soon
Wish me luck!!
The followup will be posted shortly.
I would have stabbed the abs warning lamp with a chisel 
( it’s a works truck, thankfully )
