BlakeW5

Ok, out driving the otherday and when I pulled into my destination my girlfriend notices the car was overheating (coolant boiling over). I noticed when out on the open highway my car remained cool, it was the stop and go city stuff that caused the overheating which leads me to believe the fans aren't working (just a guess I'm not sure).

So I carefully made my way to autozone and had a scan done. Here's the list with explanations:

P1642: Fan control relay 2 and 3 control circuit fault
Explanation: The ECM has detected a fault on the output driver module for the fan control relays 2 and 3.
Probable Causes: 1-Open or short circuit condition 2-Failed fan control relays

P1641: MIL control circuit fault
Explanation: The ECM has detected and open or short circuit condition on the MIL circuit
Probable causes: 1-MIL bulb condition 2-Open or short circuit condition

P1416: Air system bank 2 fault
Explanation: During the AIR system test the ECM looks for a change in O2 sensor voltage - No change was detected
Probable causes: 1- AIR pump electrical circuit fault 2-Blocked AIR system 3-Failed AIR pump

P0412: Secondary air injection system fault
Explanation: The air injection system is monitered for faults
Probable causes: 1- Circuit relay defective or fuse open 2- Check connector and wiring 3- AIR pump defective or hoses blocked.


So basically could someone explain what all this means? I'm guessing my problem is caused by a blown fuse. I checked the underhood fuse box and found that #7 (A/P - fan) was dead and changed it out. I never checked the "relays" (the black box looking things) but I'm guessing one or both and dead. How do I check to make sure they're still operational (relays D & F are for the coolant fans)?

Also, what's the MIL control circuit? What does it do, where is it located, and how do I check to see if it's dead?

Finally, I assume the AIR is also shot, but I doubt I'll bother fixing it (like I never bothered to fix the EGR). I know people delete both when they get tunes, but can it be harmful in anyway if I leave it hooked up yet malfunctioning?

Any help or suggestions are very appreciated

Z28Freak86

Well lets see if we can help you out. first off, #7 is the air pump fuse, which is 20 amps. The one right below it (#6) is the the 10 amp fan fuse. either way, its always good to check all the fuses cuz they r cheap enough.

A good explaination for why it heated up when it did is simple, the cars stock had the 180 degree thermostat, but the PCM doesnt turn on the fans till i think 215 degrees. So when your moving, the fans shouldnt kick on because the air is great enough to cool down the coolant on its own, however in stop and go traffic it will heat up till that 215 degree mark and finally turn on the fans.

However i assume that if the fans really arent kickin on and your getting those trouble codes, then the fuse and relays are a good spot to start. You will need a voltage/continuity tester for this. There are 3 relays, D,F, and J. here how to check to see if they work. On the bottom of the realy you of course have the connectors, and next to the connectors you should have numbers, (86, 30, 87middle, 87right, and 85) this will be my reference for you. First thing you would want to do is to check to see if there is no continuity between 30 and 87 right. next, you want to apply power (standard 12v) to 86 and ground out 85, then recheck for continuity between 30 and 87 right again. With power going through it, you will hear a slight audible click, and there should be continuity. If any of the relays fail this test, then its bad.

Additionally, some other things to check is if there is power getting to the relays. where the 87right socket connects to in the fuse box should always have power. where 86 connector goes into the panel, that should have power only when the key is in the on position.

Hope that helps, keep us posted!

BlakeW5

Cool. I just got done checking the relays. I didn't try it the way you suggested, but I will tomorrow maybe. I switched out the relays (2&3) with the fog light and air pump relays (they're the same). The fans came on. Then while still running, my dad switched in the "bad" relays to see if anything changed. From what we saw (the fans ran with each relay) the relays aren't actually dead. Naturally I'm low on coolant now, so I'm going to flush and refill the system and see if that helps.

All in all, I'm still not sure what caused it to overheat in the first place. Initially it seemed that the fans didn't kick on. When I was on open road and could get air flowing over the radiator it cooled down. Stop-and-go the car jumped in temp QUICK, which lead me to believe it was fan problems. Who knows, maybe there was just a freak incident that caused it and it's all back to normal now. I guess time will have to tell.

I doubt it was a result of the factory settings though. I have a 160 thermostat, and reprogrammed it with the hypertech (which also turns the fans on earlier). I'll definately check the 87 and 86 sockets though. Perhaps they weren't getting power at the time and it caused the fans to malfunction.

Injuneer

Where did you get your code list, or is P1641 a "typo"? P1641 is for the primary fan control circuit (Relay #1). Has nothing to do with the MIL (SES) light. The MIL light (aka "SES" light) failure is P1661. Or did you simply make a "typo" on that code? If you had all those codes, the SES light should have been on. If it wasn't there's a problem with the circuit that turns it on, and it could be as simple as the bulb being burned out. Check to see if the SES light turns on briefly when you turn the key to "on", then goes out after a few seconds. If you don't fix the AIR pump circuit (most likely the fuse) and the flow to the right bank, the SES light will stay on. Or, you could have the codes "programmed out" of the PCM.

The primary fan (low speed) comes on at 226*F (not 215* as indicated in a post above) and the secondary fan (high speed) comes on at 235*F.

BlakeW5

I had Autozone print out a list of the codes with descriptions. But yeah, it says P1641 is an MIL code. It makes alot more sense that it would be fan related though.

I've already fixed the airpump. It was just the fuse (the first thing I checked when I got home). So that's out of the way.

The thing that kills me is that my fans were working all that time (at least as all the relays working would suggest). I kinda suspected the waterpump too though. While I was working my way to autozone I kept the car revved up at stop lights and the engine cooled down. Given that the waterpump is driven off the cam, it would make sense to figure that the waterpump was going out and not operating at full efficiency at idle. However, I did a search on here and most every post said that a preemptive sign of water pump failure was coolant leaking from the weep hole. I checked the water pump and couldn't find any signs of leaks. I also saw suggestions to take off the inspection cover and check to see if I could turn it by hand, so I'll have to try that when I get the chance.

Injuneer

If you had the P1641 and P1642 codes, the fans would not have been working.