after driving my "99" through a rain storm and parked the car that evening, I started it the next day it seems like it is running on 3 cylinders.
the check eng. light comes on and it runs very rough. I ran the diag. test and these codes came up.
10pcm: p0351c,p0354c,p0356,p057
a6-scm: u1255,u1160,u1016,u1064

 

Well
First of all welcome to the forum, Now

Your probably running on more like 4 cylinders.
Your throwing codes for ignition coil circuit malfunctions A, D, F, and G. Thats the P codes, sorry I cant help you with the other ones.
Just how bad of a rain storm was this?
man bro' this makes me not want to drive my car in the rain. Do you have a Cold Air Intake on your car?

 

I sounds like one of your coil packs got soaked, water leaks, etc. Could be a bunch of water got up under one of the plastic covers over the coil packs. The coil wiring looms or the plug wires themselves can get old and brittle. I'd take the covers off and inspect everything. If you have the original plug wires (going on seven years old now) I'd replace all eight. Them try it. If that doesn't work, I'd try drying the coils and wires to them out (time will maybe do the trick, or a hairdryer). Be careful there is some nasty voltage in the plug wires -- they can bite!

 

thanks for the responce.
just came in from working on it. I found 4 different grounding in the engine compartment. 1 behind each headlight, 1 under the ECM/batterie. And one on the driver side just to the side of the engine, which is still corroded and has to be cleaned.
I checked the plug wires and they seemed ok. I do plan on replacing the plugs, any idea where i can find a deal on wires?

Dave

 

The P0351, 4, 6, & 7 refer to coil circuit problems on those cylinders 1, 4, 6, & 7 and the PCM has shut down the injectors on those cylinders as to not put out bad emmisions. The U codes are all buss communication codes and I don't have my Alldata in front of me to tell what they refer too. More than likely you might have got water in the connectors to the coil packs and possibly shorted coils. Unplug coil connectors and take some air and blow out connectors and coil plugs 1st. Ohm test your coils on those cylinders compared to the others and see if they are bad.

 

To all that responded to my problem

First of all thanks for all your responses, this is what was found.
After checking the coils and replacing all spark plugs I took it to a dealer to have it diagnosed. This is what they found.
Behind the right front tire is a panel which is where the PCM is located. The tech found a cracked shield from a rock hitting it. This caused water to enter into this compartment.
One of the two plugs (blue), which plugs into the bottom of the PCM, was so corroded that it was shorting out and causing the rough running. The shield was the part that was corroded and was almost gone.
The dealer wanted to replace the entire wiring harness and PCM and shield at a cost of $2900.00. That is if he didn’t have pull the engine.
I disconnected the connectors cleaned them, and put silicone around the plugs and reinstalled them. All in all this placement of the PCM was a pour design by GM.
I’m back on the road.
Thanks
Dave Parsons

 

To all that responded to my problem

First of all thanks for all your responses, this is what was found.
After checking the coils and replacing all spark plugs I took it to a dealer to have it diagnosed. This is what they found.
Behind the right front tire is a panel which is where the PCM is located. The tech found a cracked shield from a rock hitting it. This caused water to enter into this compartment.
One of the two plugs (blue), which plugs into the bottom of the PCM, was so corroded that it was shorting out and causing the rough running. The shield was the part that was corroded and was almost gone.
The dealer wanted to replace the entire wiring harness and PCM and shield at a cost of $2900.00. That is if he didn’t have pull the engine.
I disconnected the connectors cleaned them, and put silicone around the plugs and reinstalled them. All in all this placement of the PCM was a pour design by GM.
I’m back on the road.
Thanks
Dave Parsons

 

Well I'm glad your back on the road, and I'm glad you didn't have to pay the $2900.00.
That could be a little painful

 

Nothing like fixing a problem for free (or close to it) that somebody else wanted to charge you $3K to do. Good to hear you are back on the road.

 

The dealer is always going to try and sell you everything they can, because they figure they will only see you once or twice. So the status quo is soakem while u gotem. []