No Tach, Speedo or gas gauge, HELP

94 XJ, 4.0L, 4wd, NP-231, AW4 automatic.

I lost my Tach, speedo and gas gauge. The tach and speedo set at zero, the gas gauge is pegged past full and the low fuel light comes on. Oil pressure, temp and voltage gauges all seem to work fine. The ECU is not throwing a speed sensor code.

I have a fluid leak at the speedometer/speed sensor connection on the transfer case but no sensor code leads me to think the signal is getting to the ECU. I can't find any blown fuses under the dash or under the hood. I pulled the instrument cluster and there are no obviuos burns on the printed circuit and the wire connections are clean and tight. The part that seems weird is the gas gauge. Should or is the gas gauge on the same circuit as the speedo/tach? am i looking for a bad ground somewhere do i have a dead instrument cluster?

Come on Guys...No one has any ideas?

lift? sye? recently serviced transfer case? my best advice is to pull the speed sensor/gear check and replace the o-ring and check your tooth count on speedo gear and make sure the sensor is lined up properly and place back in, this should cure your problem, if not pull out and try a different position..may take a few times

3.5" RE lift, no SYE and no Vibes. Nothing has been done to the transfer case recently. I'll pull the sensor and reposition it but i think if it wasn't sending a signal i should be getting a code from the ECU, at least that's what the useless Haynes manual says.

Well, if it was a 97+ the first thing I would tell you to do is pull the IP and clean the connector and use a little dielectric grease on it. Might do that and pull the connector from the PCM and clean/dielectric grease it too.

Tach signal is generated from the CPS via the ECU, not from the VSS, so what you have here is 3 different gauges driven by 3 different senders in 3 different sections of the vehicle+wiring harness acting up at once. I would suspect the wiring harness (the one along the back of the dash, it's the only one that's really common to all these faults) and/or power and ground to the instrument cluster.

So 3 different senders, do they all report to the ECU first then the gauge cluster? If so that means it's between the ECU and the gauges right? I am not the best spark chaser there is so tell me if i'm right here. The ECU is the black box btween the air filter box and the fender on the drivers side right?

I have taken the gauge cluster out and the wire bundle that comes to it goes back into the dash assebly right behind the gauges. Does it go straight through the firewall from there or does it run along the inside before penetrating the FW?

Does anyone know if it is one harness between the ECU and the gauge cluster? if so are there any plug connections in between the two or is there just a plug at each end. If i remove the air box can i open the ECU and check connections or is it a sealed, do not open under penalty of instant meltdown type of component?

The signal from the cps goes to the ecu and then to the gauge cluster via the engine harness and dash harness. The signal from the vss goes direct to the cluster via the trans harness, engine harness, and dash harness iirc though it may also go to the ecu for cruise control. The signal from the fuel level sender to the cluster is direct though, just body and dash harnesses for that one.

so i have 3 senders with multiple harnesses. it sounds like the only commonality is the dash harness and the gauge cluster itself. I guess if i cant find any bad connections i might try a new cluster. Does that sound reasonable?

Sounds like a plan to me. My course of action would be checking grounds, checking power wires, checking the connector at the cluster, then replacing the cluster. Should cost about 30 at most self serve junkyards, aim for one with close mileage to your original as it's not easy to set the odometer to the proper value on 91-96 (90 and earlier are easy.)

Actually, now that I think about it, the odo and speedo are taken from the same signal, the vss. Do they both not work or only the speedo? Only one would indicate a cluster failure to me.

Tach and speedo are both dead. Does the Tach take signal from the VSS or the CPS?

Tach pulls signal from the CPS via the ECU (since the CPS signal has to be converted to something the tach can understand)... I think I said that already, not sure.

Sounds like the big, multi-conductor plug on the back ot the cluster is loose. Try pulling out the cluster, and snap the plug back in again.
Now for the bad news. The last time one of ours acted like this, the alternator was porked. It started with dirty battery terminals, as it was easier for my son to pop the hood, and tap on the connectors to start the car than it was to actually clean them. Soon, the battery was dead. Not long after that, the alternator was gone. All the while, the gauges acted funky. Soon, he learned a few choice new words, because it was yours truly who learned what a swell spot the alternator is in!
Try the connector at the back of the cluster, and if that doesn't work, have the output of the alternator checked. Many times, they'll fail softly, leaving only small clues along the way.

Every once in a while if I hit a bump I'll lose the speedometer and tach; left alone they would eventually come back up (anywhere from 10 to 30 secs). Would happen every day or so. Last few times it happened I whacked the side of the dashboard and they came back up immediately. It's happened enough times, with me varying how long I wait to whack it, to know it's probably the connecter(s) on the back of the cluster.

This past weekend I pushed the portion of the wiring harness that goes to the dashboard in toward the dash and put new tie wraps along the harness running across the firewall to slightly reposition it and tighten it up. Have not had a single occurrance of losing the instruments since. I still need to get behind the cluster and verify the connection, but I think it'll be okay.