Hi there,
I’ve been having trouble with the ABS system in my 1989 XJS convertible. The ABS worked up until about 6 months ago, where the light would occasionally turn on, usually after about half an hour of driving. Before the light came on the ABS would work fine. The brake fluid has never been low, and I’ve never had any issues with the brakes being too weak. Then about a month ago the light would not turn off at all after the car was started. I found the test procedure for the ABS on these forums somewhere, and so I shorted the test terminals and the light stayed solid, which the test procedure indicated ECM replacement. I’ve replaced the ECM with a second hand one I purchased on eBay, which initially turned the light off, but soon after it did the same thing with the solid light. This time however, when I shorted the test terminals, it flashed one code: 21. I’ve checked the resistance of the main valve solenoid which is 3.1 ohms, and there are no shorts to Earth that I can find. I do not know how to proceed, and am struggling to find the relevant literature; the test procedure I have just states fault in wiring/ECM/main valve/power transistor. Does anyone have experience with a similar issue or a good test procedure which can help me?
Thanks in advance for any help,
Ben

 

Hi Ben

Have a look at this: Testing the ABS Valve Block on a 1989/1990 XJS V12 (Video)

If one of the Valves isn't 'Clicking' then it could be a Broken Ribbon Wire inside the Valve Block, which is a very easy and inexpensive Fix

Good Luck

Alex

 

Ben.

Before you go any further, did you run the ECM memory erase cycle? This is really important as the blink test procedure can not display more than one code of the same group at a time.

For example, it displayed a 21 code, but it can't then tell you that you've also got a 22 code until you've erased the 21 code.

Codes 22 to 27 relate to the individual solenoid valves, so you need to clear down the 21 code and then see if you've got another 20-series code, note that, clear it, run it again etc. This way, you'll work out where the real problem lies.

You really need to do the analysis first before you start any work on the system.

Good luck

Paul

 

How do you do that? The literature I have only states the codes are cleared when the brakes are operated above 15mph.
Ben

 

Ben,

It needs to be driven above 30kmh / 19mph

Paul

 

Hi Paul,
I’ve done that though 21 still shows.
Ben

 

Ben,

I would start by checking for a short in each of the inlet and outlet abs valves.

Paul

 

This. it's probably in one of the ribbon connections. Follow Orangeblossoms thread. You have the same fault code I did.

 

Is there a link to the diagnostic procedure? Iv read mentions of it but never had a step by step. My car dives to the right occasionally, the abs unit was cleaned at last trip to tge shop but no parts/wireing were redone. Naturally the issue came back

 

Hi VancouverXJ6,

Hopefully the attached will help in tracking down ALBS faults. Not sure if there are any differences between 6 and 12 cylinder models. Hope it helps.

Cheers,
LeeP

 

Hi there,
I completed the test as shown in the video, all the valves seemed to click no problems in the valve block, I ran the car up and down the road to clear the code and rechecked but it still shows 21.
Ben

 

Code 21 is right front wheel speed sensor. Ask me how I know. I would start by separating the connectors on the inner wing and test the sensor for continuity. If good, spin the wheel and see how many volts it kicks out. You can compare it with the other front sensor readings on the other side.

 

Front right sensor problems are Codes 32,36 or 42, as far as I recall from documentation? Not sure why a Code 21 would be front right sensor, brinny?

Paul

 

Your right. 31 sensor fault.