Bcm causes cluster issues?

i get an immediate overheat message on dash when I first start motor. on cold motor? says a/c is off due to overheat. pontiac likes messages i guess. so, where do i go next? engine bay has no coolant spray like motor was hot. coolant jug is full. no scuz from overheating. i drove it for 10 min and temp gauge is at stone cold. and tach needle is pointing straight down. like off the dial. is this an elec issue? bad cluster? Bcm?

Looks like a problem in the cluster.

When I turn on ignition I can make the tach needle move a bit. It goes from straight down to maybe 530 position or so. It does move so I think it is attached to center pin shaft. Gas gauge works. ?

I have zero info on this car or the way its cluster works, but generally when a temp gauge or a gas gauge goes straight to the top with the key on, it means there’s a full 12 volts to the gauge instead of the lower voltage that comes through the sensor. That’s the old school system; this might be some sort of computerized set-up. I would probably try to take the cluster out and see if the connectors are all hooked up fully and if wiggling any wires changes things.

There’s probably some sort of sensor that sends info on the revs to a computer that them sends that info to the tach, but electronic systems like that are way past my knowledge.

Try searching a forum dedicated to GM stuff.

If you look at pic you may see tach cannot drop down below 0. There is a molded curve in bezel. Tach needle has to go fully beyond 8k in clockwise rotation to get to where it is now. What might make needle go beyond full circle? Lightening. Strike? Battery short? I am going to take out cluster and see if I can rotate needle back to 0.

The cluster is a computer itself. It makes all the calculations and drives the needles. I’d suggest the cluster itself is bad.

Is the overheat message and wonky tach related? Or a coincidence?

The overheat warning is created inside the cluster based it what it reads processed by the cluster. Good sensor, bad cluster, bad readings. The wonky tach takes its commands from the what the cluster tells it. If the cluster itself is bad, it could cause both.

Is it true swapping the cluster may cause start/security issues? Do I do a hot swap? IGN on? Disconnect battery? What’s the procedure?

I can’t think of a reason why swapping the cluster would cause start or security issues. But, I would NEVER hot swap anything that has to do with electronics. Remove the positive battery cable first.


In some models, not necessarily this one, the instrument cluster is programmed with the VIN, and must appear on the bus for proper function of the security system. From time to time, we see posts from people who installed a junkyard cluster, and discovered problems ranging from annoying (odometer reading won’t update, etc) to serious (no start, anti-theft light stays on).

In some models, such as the 1996-2000 Chrysler minivans, the instrument cluster serves as a “hub” for the communication bus, and if defective can result in no start. There was a problem where cracked solder joints on the circuit board on these clusters resulted in erratic operation or no starting.

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Took out cluster. Takes 5 min. Lifted up lens and rotated needle to zero, I could feel the stepper motor resistance. Started motor and tach works now. Goes to zero with motor off. Messages still say hot motor. I did unplug temp sensor and forgot to plug it back in. No new messages. Due to missing temp info? Might drive it around today to see if motor gets hot.
I have 2nd equinox but I am not going to borrow.a good sensor. And get coolant all over.

@bcohen2010 has it right. The cluster contains vehicle specific data and swapping it may cause a no start.

I am doing that right now with my Mustang. I am installing a Track App enabled cluster from a year newer car. The security system that identifies the keys will prevent a start. I have software that can program my 2 keys into the new cluster. I will also need to change some other things to enable the Track Apps as well as set the odometer to the correct value. The dealer can do this, too.

It’s highly likely the stepper motor for the tach is faulty . . . don’t be surprised if the problem reoccurs

Went to store. Used code reader. No codes. Cel light is on. Abs light is on. Tcs light is on. Temp gauge is cold. Message center says motor overheat. Either bad cluster or bcm. But speedo works. Tach works.
It was 90f today. Motor is not overheating.

If the bcm and ecm are good would a bad cluster make the ac stay off? Since the cluster is saying motor is hot/ac off? Suv drives fine as is. But I really want ac in July.

As for the “a/c is off due to overheat” . . . I have some information that pertains to GM vehicles specifically

If the pcm believes that the coolant temperature is beyond a certain threshold, the ac compressor clutch will be prevented from engaging

Obviously, there are several reasons why the pcm might believe that

We had a few GM vehicles in our fleet . . . not the same as yours, but the same vintage . . . that also had this exact phenomenon

We were able to determine that the engine coolant temperature was well within specs

We were also able to determine . . . with a laser thermometer and ohmmeter . . . that the coolant temperature sensor was working perfectly

Next we simulated specific temperatures with a decade resistance box

And that is where things got interesting

The pcm did not “see” the temperatures we were simulating

Next thing . . . wiring diagram(s)

In the end, we were able to physically see that one of the two pins on the pcm . . . the ones for the engine coolant temperature sensor . . . was physically burnt off of the circuit board

Eventually we found that a certain wire was barely chafed through . . .

And by further looking at the wiring diagram, we were able to determine that particular circuit was unfused, meaning when that wire touched metal or whatever it was . . . it was a little while back . . . something was going to give, and it was the pcm

In the end, the only possibility was live with it . . . and all the warnings . . . or replace the pcm, get it programmed and fix that wire

No offense to anybody, but my gut feeling is it’s not the cluster causing this, as far as this Torrent goes

fyi . . . the GM vehicles in our fleet with the identical problem. The cluster also read stone cold, while at the same time the message center said engine hot, ac disabled


There are lots of people reporting bad gauges and tachs of this era GM products if you search Google for Torrant gauges cluster. Somewhere in all that you might find a definitive answer.

A bad stepper motor will not cause “engine hot ac disabled”

The ecM is on top of battery box. It’s about 1 ft from temp sender. Are you saying the wire harness from ecm to sender has a frayed wire? And the ecm may have a bad component? Can I swap out the ecm for a used one? Same year rig?