1997 camaro p1651, p1652

I'll post this evening with results. thanks for the info

at 225 pcm gave command to turn on fan 1 at 230 pcm gave command to turn on fan 2 no fans were operating. checking voltage with volt meter; 13.88 on on wires that are fusedwhich by the schematics is OK checked grounds at relays and at fans OK. now for my question?? dark green and lt blue wires from pcm have 13.88 volts when command is given. you can not hear relays clicking. now if i take a simple test light on the back of the fuse panel to the pcm wires the voltage will drop to apprx. 6.5 volts and the relays click and high speed fan turns and cools engine. why would a test light drop voltage on these wires and cause the fan to work? how much voltage should be present on the 2 pcm wires? also it sounds like the grounds can't be ok. my test light is probably the shortest path for the pcm wires to make a ground, and that might be why the voltage drops and the fans kick on? why would you want your fans turning on at 225, 230 seems awful hot to me.

Okay thanks for doing that, but it's important. Im very busy at work this am, but I'll look at the diagram and try very hard to post back for you today sometime. I love a good wiring problem!

Okay just so I understand: With your test light intalled to ground you probed the dark green wire(Fan 1 command) and dark bluewire(fan 2 command) with the relays plugged in and the fans activated. Okay if that is what you did I'll try to explain the best I can. 1. The reason your test light lit up is because there are electrons running through it. It's counterintuitive, I know, but think in terms of electrons flowing. Electrons are very high strung. They are trying to race from negative to positive terminal so they can relax. The negative terminal has a great # of elec. and the positive has none. They want to get to positive. When you hook up your test light to ground and then probe the dk. green or dk. blue wire, the electrons race from the negative post you clipped to, through your light bulb in the test light, and into the ground wire, and continue to the relays coil, the other side of which has a 12 Volt POSITIVE feed. I know it can be confusing when that happens, but the wire you are touching with the test light does NOT have 12 V. I can actually recall asking that very question when I was younger. If you had used a voltmeter connected to ground and then touched that terminal,you wouldn't have seen that voltage. 2. The reason touching that terminal turned on the fans was because your test light became the PCM command circuit. YOU and your test light completed the ground that the PCM is evidently not completing, and voila, turned on the fans. At this point: If I had the car in my shop and I know what we konw about your car, this is what I would do. Make sure that the wiring integrity is okay from the PCM's command circuit to the relay's coil. I'll tell you how to do it. You know which wires they are? The dark green(for fan relay 1) and the dark blue(for fan relay 2 and 3). Go to the PCM connector labeled C1. Find your two wires. To do this properly, you'll have to remove those two individual wires from the connector. To do that unpluge the connector and remove the retainer. IT's a plastic sliding peice that should be a different color. It retains the wires, so they can't be removed without it's removal. Remove it, and now you're halfway there. Looking into the connector you'll see the terminal for the wire. There's another spring clip holding the terminal in the connector. You'll have to reachin there with a special small tool to release the wire. Now with the wires out(only the two mentioned above) turn ignition ON, engine OFF. Now you can ground the PCM circuits without the PCM in the loop. If the fans operate when they are grounded, all your wiring is okay, and not broken, and you're looking at having to replace the PCM. Again, This isn't beginner stuff! It takes special tools and some know how. So don't feel bad if you feel like taking it to ashop, okay? This stuff can be difficult and mind bending at times! It's most likely a failed PCM, but take heart! you just diagnosed your first PCM failure. I know COmp is gonna let me have it for giving such info to the general public. Sorry Comp! Now, I can't stress this enough. DON"T USE A TEST LIGHT anymore when working on or around PCM driver circuits. Get a volt meter from now on, okay? You'll appreciate it later. Some circuits it won't hurt, others can be damaged by the feed back of voltage into the computers driver circuit(like when your test light glowed).

with OUT the test light and just a volt meter , all relays hooked up, engine running and tempp at 225 and 230F. there was 13.88 volts at the blue and green pcm wires on the back side of the relay.

I'm not going to let you have it! Im just not the hand holding type! guess 1 of us should be though!

Hmmmmm. If the voltage appears only when the PCM commands the fans on, then there's a PCM failure. IT's internally shorted on that driver. To be sure: disconnect the aforementioned wires out of the connector(as per instructions above) plug PCM connector back in and see if the voltage returns as before. There shouldn't be voltage on that circuit. If the voltage returns with wires disconnected=there's a short to voltage somewhere. (But it'd be a heck of a coincidence). IF the voltage doesn't return=PCM is failed by applying voltage to a ground circuit. Sorry, dude, but it doesn't look good.

thanks I,ll post results

Darkrooms, THANKS! all circuits to the fans are working. once i disconnected c1 at pcm i took and checked for continuity from #31 #32 (drk grn and drk blue wires) none present. followed both wires found the brake and soldiered wires and heat shrinked. everything is up to snuf. Thanks again

Why you'd have thought it?

Your welcome, Mcgeek, glad we all could help you. And glad your problem is fixed!

I've been having issues very similar to this and have been receiving the p1651 code. It starts ok, but while driving, it loses power, sputters and popping while accelerating. I also have the ABS inop. illuminated. Also, the air conditioning clutch isn't engaging when turned on (may or may not be related). I Have tested pin 31 and have continuity to the relay and I can engage the fan when shorting the relay terminals. Going to test the dark blue wire for continuity in the morning. I do have an extra parts car with a good PCM I can salvage, if it come to that. I'm wondering if it could be the Fuel Pressure Regulator. In the past I have changed the plugs and wires which improved things for a couple days, but then all the problems resumed. I know this post is old, but I'm hoping you guys are still around for help. thanks, Joe

Joe start a new post, Year, Make , model, engine, MODIFICATIONS, and all codes, describe issues.