Bottom line up front:

Last night my wife's '00 B4C threw 2 codes:

P0300 Engine Misfire (common code on our cars, not the one I'm worried about)

P1637 Generator L-Terminal Circuit

What component is typically failing when the P1637 is thrown? I need to fix this ASAP to go back to the track for the shootout tomorrow night.

I strongly suspect a problem with the alternator, but I will post the whole story to "help you to help me".

Last night I took my wife's nearly stock 2000 B4C Camaro to San Antonio Raceway. I had just installed a UMI Torque Arm the night before and wanted to test the effect on traction (it worked great BTW, car dead hooked).

First 2 passes were normal. Car ran an acceptable ET and Trap for the warm, humid air. 3rd pass the car felt like it was falling off a little before gear shifts (it's an A4) and indeed it ran a little over a tenth slower. With the great traction, a variance like that with this car is an anomoly. I was scratching my head a little, but decided to just do another pass after a cool down and see what would happen. Well, on the fourth pass the car was falling off big time in the upper RPM band right before the shifts. Almost like valve float or a clogged fuel filter. However, the car is nearly stock and shifts at about 6000 and the fuel filter was replaced recently. I reached the traps and my SES light comes on - FLASHING - I quickly scan my gauges as I reach for the ignition key to kill the motor. Gauges are normal, so I leave the motor running and come back up the return road. I get my timeslip and the car slowed down by 4 tenths!

I park in the pits and grab a flashlight. Can't see anything wrong. I fire the car back up and rev it lightly a few times. The SES light is on, but not flashing. I decide that a sensor or injector or something is FUBAR'd so I leave the track. I linked up with a buddy on the way home and he pulled the codes which I posted above.

I am suspecting the alternator for several reasons, but want input from anyone who has battled a P1637 code before.

1. The car is an ex-Colorado Highway Patrol interceptor and has 111K miles. The alternator and electrical system have been taxed just a wee bit more than your "average" car. I do not know how old the current alternator is.

2. Occasionally the car seems to have an unstable voltage output. The lights will flicker (slightly, not "strobing", more like pulsing) and the needle on the gauge will wiggle. This only happens every once in a while and I chalked it up to the police mechanics leaving a ground wire or something loose when they pulled the police gear out of the car. I have checked the alternator connections and they were good. Haven't had time to pull the car apart for what has (in the past at least) seemed like a minor annoyance.

3. The volt gauge needle stands straight up at 13 when idling. My other LS1 cars read about 14.

My theory is that the voltage regulator in the alternator is going out, or the whole alternator itself. It is unable to provide enought current at high RPMs to fire the ignition that rapidly. This would explain the misfire code and the engine falling off at high (er) RPM. The plugs were simply not getting enough spark or getting spark but not quickly enough.

Please post up your thoughts. If I don't get any other good input, I'll just swap out the alternator and see what happens.

THANKS in advance.

 

You had an open circuit on the L terminal of the alternator. May have been just a random thing. Might try to clear the code and see if it comes back. If so....you have a short somewhere in that circuit. I think.

 

Thanks Tony! I was about to email you a link to this.

We already cleared the code. I drove the rest of the way home ~25 more miles and it didn't come back on.

Anyone else have some thoughts?

 

Anyone else?

Took the car by Autozone ( I know, I know, ) and had them put their alternator tester on it... checked out fine.

Need some advice on what to check.

 

I had the code 1637, it turned out to be my Skip Shift elimnator. I took it off the car, and it's been fine ever since.

I didn't need it on my car anyways, since I removed it via the PCM.

 

Hmmm... shouldn't apply in my case... it's an A4.

But, thanks!

 

Get that terminal replaced ASAP. I kept getting that code and erasing it thinking it was nothing major. Since that wire has hardly any play, the code would keep coming back faster and faster until it just snapped right off and left me stranded. I got a replacement for about $35 at the dealership. The one they gave me has four wires, just cut off the ones you don't need and leave enough slack on the new one. No 1637 code since.

 

Where? Which one?



Thanks.

 

The one on top of the alternator.

 

bringin back from dead, but do u know the part number for the replacement plug thing for the alt?

 

I don't remember, but all I did was ask for the plug on top of the alternator and they knew what I was talking about........