'97 Grand Prix low coolant sensor issue...

Problem started with a P1651 code, realized then the cooling fans weren't working. Checked relays, cooling fans, replaced the Coolant Temp sensor, all good there. Before starting the car (key in on position) all warning lights are on EXCEPT the low coolant light. Shouldn't it be?! Is it possible the sensor is bad and interrupting the circuit for the Cooling Fan relay? Can something as simple as a burned out dash light for the same sensor do the same??...or should I be tracing down all the grounds related to the fan circuit from the ECM?! PLEASE help! (so my kid can stop driving my car!):crying:

The coolant level sensor has nothing to do with the cooling fans. The low coolant lamp doesn't lamp test like the other idiot lights at the IP cluster. The PCM module controls fan turn based on input from the ECT (engine coolant temperature) sensor.

What happens when you disconnect the ECT sensor and then start the engine. Both fans should turn on in fail safe mode within several seconds of starting the engine.

The P1651 DTC is a cooling fan 1 relay issue.

Thanks for the response BNaylor, and thanks for clearing up the dash light question I had. I did as you said and only the cooling fan 2 came on after unplugging the temp sensor. While it was running I checked the relays (switching a known good one to the spot labeled for the cooling fan 1) and cannot hear the relay operating, so I'm guessing there is an iterruption somewhere in the wiring, yes? Electrial diagnostics have never been my strong point, but as long as I've been turning wrenches you'd think I'd be better at it. A little embarrassing, and VERY frustrating...but I am trying to learn (and not give up) on this issue. Any direction or tips? I have a wiring diagram in a Haynes Manual, but not as clearly formatted as the Shop Key diagrams I've viewed in the past..:banghead:

Thanks for the update. Wiring is possible. The issue appears to be from the output of the PCM module to cooling fan relay #1 at the engine compartment fuse box. I'll check to see what pins at the socket are used. The PCM provides a low/ground to the cooling fan relay. The relay always has 12 volts on one side of the coil.

Also, check the maxi fuse to cooling fan 1. Fuse 6 (COOL FAN 1 - 30 A).

Fuse is good, double checked it anyway.. For the record, the ABS, Trac Control, and Tire pressure lights are on (and I was assuming these were a result of a questionable ABS sensor), but after reading about all the GP wiring issues people have had, do you think all these issues could possibly be coming from the wiring harness from the PCM rubbing under the air cleaner box that I've been seeing periodically on different posts? BTW, maybe a non-issue, but in keeping with forum guidlines this is a high mileage beauty (170,000 mi.) GT, 3800 motor.

There should be a lot of life left in this one.

I would say your ABS, traction control and tire pressure warning issues are unrelated but you never know for sure. Wiring is a possibility but probably more so at the engine compartment fuse box area. You could get that issue looked at with an ABS capable scanner since it could be any wheel sensor, electrical connector, wiring or even the ABS module aka EBTCM module.

On the cooling fan issue you can ohm out with a multimeter point to point the output from the PCM module to cooling fan relay #1. Also, put a fused jumper at the relay socket contacts portion of the relay to see if the cooling fan turns on just to rule out the output of the relay to the respective cooling fan. The pins are marked on the relay and you can compare it against the relay socket.

So THAT is what the numbers on the relay represent! I pulled the air cleaner box, all wiring looks intact. I have clear access to the pcm now. I used a test light and found power at two terminals of the relay and when probing the other two terminals one of them powered up the fan (ect unplugged for 'fail safe' mode, relay semi installed)..I believe it was pin #86. I shall ohm out 'both' the wires that have no power at them and see where I'm at then. As far as the abs issues I'll see if I can use a friends Modus again to check the signals at the sensors. I appreciate all your help, and will be sure to try to contribute to others on this site where I can. I'll let you know how it went...