ellardpa

Hi All,

Brand new to the forum - although I have used it quite often as a "lurker" .

I bought an 86 GXL a couple years ago. When I bought it, the previous owner had the power steering bypassed. Last year, I decided to reinstall it, and upon doing so, it would only run in "full" boost mode no matter the speed. This year when I fired it back up, the speed sensitive steering did work properly, but it only lasted a few drives before going back to full boost 100% of the time.

After doing some research, I decided to grab a used power steering control module computer (DZ-A01) thinking that it might be a cheap fix to my issues. Unfortunately, after installing it last weekend, I still have the same problem.

I suppose it's possible they both have the same issue (main problem seems to be failed solder joints), but are there any other troubleshooting tips for this issue?

Thanks in advance.

WondrousBread

The speed sensing steering is one of my favourite parts of the car. Unfortunately it's also a complicated system, so troubleshooting it can be a whole can of worms.

First, you should download the relevant section of the training manual from Foxed.ca. I have attached it to this post for you as well. The entire thing is a fascinating read, but the page you will likely need most is this one:


You'll notice that none of these failure modes involve 100% assist. I have had a power steering computer that was D.O.A, and it did exactly what you described. No noise, no steering control, nothing. This is because the "resting" position of the stepper motor on the power-steering pump is the idle position, which is 100% assist.

I swapped in another computer and it worked fine. Normally, the computer should beep to notify you of the error it's detecting. The fact that it isn't beeping (as implied by your post) means the computer is either not connected, or the power to it is intermittent. The fact that you have two computers makes it unlikely they are both dead.

I would download the wiring diagrams (also at Foxed.ca) and find the diagram for the PS computer connector, and start checking the pins to make sure power and ground are present. If both are there, the computer should at least be doing something. Either working, working partially and beeping, or just plain beeping. Also inspect the wiring for any visible damage. As we all know, previous owners tend to find new and unusual ways to break the car.

ellardpa

Thanks for the reply and info, I will try your suggestions this weekend!

You're correct, there are no beeps specific to the lack of speed-control (sorry should've stated that in the first post). The original owner had a wheel off a Miata, with a makeshift steering wheel cam which wasn't working properly - which then caused the power steering computer to beep (abnormal steering angle alarm). I have since fixed that and installed an OEM cam/wheel, so no more beeps related to that.

So the computer is definitely doing "something", but perhaps it's not reliably receiving the correct signals for the speed-sensitive functions. Just can't explain the lack of beeping or the intermittent functionality of the system...

Thanks again!

WondrousBread

One thing that comes to mind is that the speed sensor might be dirty.

I recently cleaned mine. I have all the pictures but have yet to actually post them. Basically, a leaky seal on the speedo drive caused transmission fluid to wick through the cable into the back of the speedometer on the cluster. This had been leaking a long time and the gunk built up on the reed switch for the VSS signal.

It only recently got bad enough for the computer to start beeping at me, but after cleaning it the steering assist is dialed back much earlier. This tells me that the missing pulses were causing the speed sensing function to perceive a lower speed, but not to cause a code to beep. My MS3X logs also now show my speed higher than it actually is, and it's calculated based on pulses / km, so clearly the number of pulses has increased.

The PS computer error code mention "abnormal" signal, but since the PS computer doesn't know what gear you're in, I can't think of how they would actually determine whether a signal was abnormal or not.

It may or not be the same issue (and it's hard to test unless you have a good way to capture the pulses and analyze them), but you should look at the back of the cluster and see if there's any oil.

ellardpa

Interesting - I will certainly give that a shot as well. Thanks again for the suggestions.