TCS/ABS/Slip Lights - HELP!

[JackJ217]

Hi all, new to the forum and a first time Infiniti owner. Just picked up an (almost) mint condition 91 Q45. So far all I've done is a new battery and alternator, as both were bad. I have searched around the forum and haven't found a straight answer for my specific problems. Also briefly looked through the online service manual and wasn't able to come up with a solution.It has 3 lights on the dash - slip, tcs off, and abs. It also has a transmission malfunction warning.
 
Self diag on the ECU displays code 54, PCM/TCM communication line open or short. The TCS control unit (in the trunk, by the LR speaker) displays code 10 - ABS actuator solenoid valve relay circuit malfunction.The TCM/ABS control unit (above the glovebox) displays code 34 - power supply circuit (for sensor) - not sure which sensor it is referring to.

I replaced the ABS actuator relay, but nothing has changed.

The speedometer also does not work - at highway speeds it randomly (not erratically, though) moves around between 100 all the way up to over 160. I hooked up my boss's old OBD1 scan tool which showed me a DTC for the revolution sensor or circuit, which I then used the scan tool to verify that the speed sensor is sending an accurate reading during a road test, both in the VSS data section and mph section. -- I also haven't seen any obvious breaks in the wires or loose connections. So, I'm not sure why there would be a code for that sensor as it seems it is working properly, other than the speedometer not receiving an accurate signal. This code did not pop up during the self diag procedure on the ecu.

Another issue is that I cannot manually shift it into 2nd or 1st, but I verified with the scan tool that it is automatically shifting through all the gears, including first when the kickdown switch is activated.

How many of these issues are related, and what should my next steps be to diagnose the cause? I'm assuming the three warning lights stem from the same problem. Could the speedometer problem be caused by the same issue? I'm not too concerned with the manual shifting issue, as I don't want to throw too many parts at this car, as I probably won't keep it for too long. 

Any help is greatly appreciated!

[VStar650CL]

There's no code 34 on the ABS. It could be 3 and 4, but those both apply to the rear wheel actuator. You can find the code list on page BR-42 (PDF page 843), the wiring schematic on BR-45 (PDF 846), and the specific diagnostic procedure for 3 and 4 on BR-50 (PDF 851):
https://www.nicoclub.com/service-manual ... 2F1991.pdf

[VStar650CL]

PS - I'm not sure about the old Q's specifically, but on most Nissan/Infiniti products that get a speed signal from both the transmission and the ABS, the speedo will quit or wig out if either signal is faulty or absent.

[JackJ217]

There's no code 34 on the ABS. It could be 3 and 4, but those both apply to the rear wheel actuator. You can find the code list on page BR-42 (PDF page 843), the wiring schematic on BR-45 (PDF 846), and the specific diagnostic procedure for 3 and 4 on BR-50 (PDF 851):
https://www.nicoclub.com/service-manual ... 2F1991.pdf

The module above the glovebox blinked out code 34. I thought that was the ABS control module at first, but page BR-103 of the service manual says it is the TCM (throttle control module?). 3 long blinks, 4 short blinks. On page BR-104 of the service manual, there is a code 34 in the chart which says "power supply circuit (for sensor)"

[VStar650CL]

Yep, that's for the TCM and not the ABS/TCS. The diagrams show the VSS signal being read by the cluster and then rebroadcast to both the transmission and ABS, so you probably have either a bad VSS or a bad cluster. The sensor is easy to check, it should produce an AC voltage with the wheels turning which increases with speed. The cluster should also be easy to check, looks like pin 34 on the cluster Y/PU should be the signal wire to the rest of the car. With the wheels turning it should show either a 2.5V signal or about half of battery voltage depending on the signal level, but it shouldn't read 0V or battery.

[JackJ217]

Yep, that's for the TCM and not the ABS/TCS. The diagrams show the VSS signal being read by the cluster and then rebroadcast to both the transmission and ABS, so you probably have either a bad VSS or a bad cluster. The sensor is easy to check, it should produce an AC voltage with the wheels turning which increases with speed. The cluster should also be easy to check, looks like pin 34 on the cluster Y/PU should be the signal wire to the rest of the car. With the wheels turning it should show either a 2.5V signal or about half of battery voltage depending on the signal level, but it shouldn't read 0V or battery.

Alright thanks, I'll test that tomorrow after work. I am expecting the VSS to be okay, as it showed an accurate mph reading on the scan tool during a road test. Where else should I look? In another forum post with a similar issue they said to replace the two blue relays underneath the battery tray. Would that be worth a shot? I'm trying to avoid just throwing parts at it though of course.

[VStar650CL]

The wiring diagrams for the older stuff are a little hard to follow, but a no-power condition to the TCS or active suspension would probably give you slip lights. So changing a couple relays just "because" might not be a bad idea. I missed it earlier, that your scanner gets the right speed. I think that pretty much rules out a bad sensor or a bad cluster, so now you have me doing a little head-scratching. Maybe I missed something in the WD's, I'll take a closer look tomorrow.

[VStar650CL]

I think first see if any of the codes will erase, it seems likely the the TCS code isn't related to the other two. Nissan ECU's have always had a weird habit of ceasing data transmission when they throw certain codes. That's why on modern ones you often get a C1130 plus an ABS/slip lamp along with a MIL, because the ECM stops sending an engine speed signal on CAN after it throws a code. I'm wondering if your VSS isn't cutting out intermittently and causing the cluster to stop sending a speed signal, and in turn that's causing the TCM to stop talking to the engine. I think I'd see if the voltage drops out at pin 27 on the TCM (see AT-38 and 39) whenever the speedometer acts up.

[Q451990]

Does power steering drop out when the speedometer isn't working properly? Here's a thread from long long ago that might help.

speed-sensor-not-the-answer-to-ps-loss-t299603.html

[JackJ217]

Does power steering drop out when the speedometer isn't working properly? Here's a thread from long long ago that might help.

speed-sensor-not-the-answer-to-ps-loss-t299603.html

I don't have any issues with power steering.

[JackJ217]

I think first see if any of the codes will erase, it seems likely the the TCS code isn't related to the other two. Nissan ECU's have always had a weird habit of ceasing data transmission when they throw certain codes. That's why on modern ones you often get a C1130 plus an ABS/slip lamp along with a MIL, because the ECM stops sending an engine speed signal on CAN after it throws a code. I'm wondering if your VSS isn't cutting out intermittently and causing the cluster to stop sending a speed signal, and in turn that's causing the TCM to stop talking to the engine. I think I'd see if the voltage drops out at pin 27 on the TCM (see AT-38 and 39) whenever the speedometer acts up.

I tried testing the voltage from the speed sensor last night but there weren't any lifts open, so i just put it on jack stands and spun the rear wheels by hand. The highest reading I got was .2v, but it may have just not been spinning fast enough. I'll throw it up on the lift tonight after work and see if I can get a better reading while it is in drive.

Five times yesterday my speedometer came back - it's never done that before. It was accurate between 30-60 mph but anything above or below that it gradually became 5-15 mph off before it died off again. This leads me to think the speed sensor is intermittently failing or even just a loose connection somewhere.

I found a used cluster in pretty good shape from a 92 on eBay for $35 shipped, so I ordered that just to see if that could fix it. Should be here this weekend.

What is the process for clearing the lights on the dash? Also, before yesterday, the transmission malfunction warning was constantly on, even after disconnecting and reconnecting the battery. Yesterday though, it would take about ten minutes to turn back on. This morning on my 45 minute drive to school it didn't turn on at all. Maybe just clearing the rest of the lights and replacing the cluster could fix the problems, as there has never been any driveability issues. Cruise control works, power steering works, and the transmission shifts as it should.

Thanks for your help so far, hopefully I can get this figured out soon!

[VStar650CL]

Checking the sensor, you won't get much of a reading on DC volts because it's an AC signal. One leg may be grounded at the cluster, so the best check is to go across the sensor terminals with the sensor disconnected and your meter on AC volts. That way you're reading full wave instead of half wave and you'll get a better idea of whether it's stable or not. Nissan speedo sensors from that era are all magnet-amplified, and it's not uncommon for them to cut in and out when they're failing. So it may well be the VSS causing your issue and not the cluster.

I think the ECM is the only unit on the car which has a backup memory, so all the other codes should clear by doing a hard battery reset. If they come back it means the DTC condition still exists.

[JackJ217]

Checking the sensor, you won't get much of a reading on DC volts because it's an AC signal. One leg may be grounded at the cluster, so the best check is to go across the sensor terminals with the sensor disconnected and your meter on AC volts. That way you're reading full wave instead of half wave and you'll get a better idea of whether it's stable or not. Nissan speedo sensors from that era are all magnet-amplified, and it's not uncommon for them to cut in and out when they're failing. So it may well be the VSS causing your issue and not the cluster.

I think the ECM is the only unit on the car which has a backup memory, so all the other codes should clear by doing a hard battery reset. If they come back it means the DTC condition still exists.

Okay that’s good to know about the memory codes. I did actually have my multimeter set to AC volts, but I’ll get a better reading later this evening.

I just turned the car on and it said transmission malfunction, but then two seconds later it said “OK” and the warning went away. I’ve got an hour drive to work now so I’ll see if it comes back on.

[Q451990]

Have you pulled the Transmission Malfunction code(s)?

[JackJ217]

Have you pulled the Transmission Malfunction code(s)?

I haven't pulled any of the transmission codes. Is that what the "A/T check" procedure is that you can access on the screen on the bottom left of the cluster? I attempted to do that but it just said "OK" every time. The transmission malfunction warning came on about 20 minutes into my drive to work, but it stayed off during my drive home after work.

I tested the speed sensor and it seems to be working as it should. Voltage increased with wheel speed. I then tested the wire right before the TCU that goes to pin 27 and that also receives a signal that increases with wheel speed. So that means that the speedometer is receiving and sending out a signal. Soooo that leads me to believe that the speedometer just isn't interpreting the signal correctly.

The new cluster should be here this weekend, and I'm assuming that after hooking that up my speedo will work. Do any wires from the speedometer lead to the abs or tcs unit? I can't tell exactly where the rest of the wires from the speedometer lead to on the wiring diagram.

[VStar650CL]

Yep, that sounds like a right diagnosis. The sensor hardware in those clusters has been known to fail. Often it's just bad solder or leaky capacitors, so you might want to pull it apart and retouch the connector pins, plus replace any electrolytic caps which are bulgy or leaking.

[Q451990]

I haven't pulled any of the transmission codes. Is that what the "A/T check" procedure is that you can access on the screen on the bottom left of the cluster? I attempted to do that but it just said "OK" every time. The transmission malfunction warning came on about 20 minutes into my drive to work, but it stayed off during my drive home after work.

That's the one. In my experience, it'll hold the code until you run the test, then it clears the code.

I have the "transmission malfunction" message pop up at startup sometimes. It'll stay on for a couple of seconds and then flip to "OK" - but if I run the self check I think it comes back with some sort of communication error with the TCU.

[JackJ217]

The new cluster finally showed up, two days late. Plugged it in and nothing works, except for the turn signal indicators are both lit up. I smelled something burning and saw light smoke coming from the top right corner so I unhooked the battery as quickly as I could. Looked more closely at the plugs, and although they all plugged right in, two of them have different color wires going to them as well as different numbers of wires. (The new cluster came with the harness attached to it, just cut a few inches back of course) My car’s harness has a yellow plug that goes below the black box that is on the top middle section of the cluster. The new cluster had a white plug in that location, and it had two extra wires going to it, although the plugs were physically identical otherwise. The other difference was the plug on the top left, near the fuel gauge. The plugs were identical except for different wire colors and the plug in the new cluster had two fewer wires.

So, I took out the new cluster and plugged the old one back in. Same exact thing happened. Nothing worked on it besides the turn signal lights being illuminated and it began to smoke.

I’m at a complete loss now. Do I have to have all of the other interior connectors plugged back in? (Hazards, heated mirrors, window switches, etc.)

It is worth noting that the new cluster was from a 92 with tcs and without active suspension. My car has the same options, except it is a 91. Everything I have seen online has said that 90-93 clusters are interchangeable, with some potential differences between 90-91, which doesn’t matter in my case.

[JackJ217]

Yep, that sounds like a right diagnosis. The sensor hardware in those clusters has been known to fail. Often it's just bad solder or leaky capacitors, so you might want to pull it apart and retouch the connector pins, plus replace any electrolytic caps which are bulgy or leaking.

Just tried it again with the original cluster and all of the interior connectors plugged back in and no luck. I’m stumped.

[Q451990]

Ugg. That's the stuff that car guy nightmares are made of. In general, yellow plugs tend to be for ABS stuff, but I don't know for sure in this particular case. The best advice I can give is to compare the pin-outs in the factory service manual for each model, and see if you can figure out what happened. In my experience, smoke usually means ground and positive reversed somewhere.

[JackJ217]

Ugg. That's the stuff that car guy nightmares are made of. In general, yellow plugs tend to be for ABS stuff, but I don't know for sure in this particular case. The best advice I can give is to compare the pin-outs in the factory service manual for each model, and see if you can figure out what happened. In my experience, smoke usually means ground and positive reversed somewhere.

Where can I find the pinouts? I found the section about the cluster in the FSM that I accessed from the forum but the only information there is how to remove it. Would I have to find a manual for both model years?

[Q451990]

The '91 manual shows pinouts on EL-53, and some of the surrounding pages. Yes, I would compare pinouts from both years. Both manuals are available at www.infinitiservicemanual.com

[JackJ217]

I pulled apart the cluster that I bought and plugged it into the car to see where the smoke was coming from. Here is everything that it does:
Both turn signal lights are constantly powered with key off.
With key on (also with the car running) - left turn signal light turns off, right stays on.
Left turn signal switch activates the TCS and ABS lights.
Right turn signal switch activates TCS light.
Hazards activates ABS lights.
Nothing else that I do turns on any other lights, except for when I had my original cluster plugged in the diagnostic display in the bottom left corner worked. It would display the "door open" message as well as "transmission malfunction."

The cluster only smokes with the engine running. I was able to track the smoke to the top right corner behind the fuel gauge, and by dumb (very dumb) luck, my finger landed on the solder on the back of one of the diodes while I was trying to turn the cluster around. This is what is getting hot. It started to melt the solder even after just having the car running for about 30 seconds. - (From looking at my original cluster, it looks like it was starting to melt in the same way.) I'm not able to tell what this diode is or what it is connected to from the wiring diagrams. I'll see if I can attach a picture of the diode.

An idea I had, is that maybe one of the bolts that I took out while taking the interior apart to get to the cluster was a ground that is now unhooked and causing all of this. Although I don't remember seeing any grounds attached to anything that I unscrewed. If that is not the cause, then my only other guess is that the '92 cluster, although it looks completely identical to my '91, has some of the wires from the harness leading into different components, so that diode is getting powered when it shouldn't be and messing everything else up. But even then, it makes no sense that my original cluster is having the same issue.

[JackJ217]

https://imgur.com/a/Aqq37im

[VStar650CL]

Diodes only get hot from carrying too much current. Something south of the diode has to be blown in both clusters (or the cluster wiring) to be overloading the diode. Try powering up the cluster with just jumpers to the ground and ignition pins and see if it still smokes.