wheeljo2

iTrader: (2)

I have the following history & current codes showing in my diagnostic center:

P0113 - HC - IAT Sensor Circuit High Voltage
P1111 - HC - IAT Sensor Circuit Intermittent High Voltage
P1637 - H - Generator L-Terminal Circuit
U1096 - H - Loss of Communications with IPC
U1064 - H - Loss of Communications with DCM
U1016 - H - Loss of Communications with PCM
C2120 - HC - TPM System Programming Malfunction (no sensors programmed)
C1255 - H - EBCM Internal Malfunction
C1283 - H - Excessive Time To Center Steering

I cleared and reset all codes and upon start-up it tripped the following codes again:

P0113 - HC - IAT Sensor Circuit High Voltage
P1111 - HC - IAT Sensor Circuit Intermittent High Voltage
P1637 - H - Generator L-Terminal Circuit

Symptoms:

Fuel trims are pegged at 25%, high voltage circuits are IAT & MAF, more often than not throttle is sticking at 2,000-2,200 rpm in neutral with the gas off, was getting some foam like substance under my valve covers so i pulled the heads and replaced the head gaskets.

Had Felpro 1041's and replaced with 6.0 LS2 multi-layer steel and installed ARP head bolts. Heads checked out fine and no evidence of leakage across gasket surfaces. Stage III LS1 853 castings with 2.05/1.57 valves. Block appears to be ALUMINUM (casting unknown) but has a 4" Lunati crank and 4.08 bore with JE forged pistons. I replaced the O2s, TPS, IAT, and MAP sensors. The computer tuning is a baseline tune for my engine and mods performed by PCM4LESS. Erratic idle control came after tuning and I was told it needed to be fine tuned by adding more "idle air decay".

Looking for your thoughts, suggestions, helpful hints, etc...as my patience is running thin.

Rhino79

iTrader: (7)

Try unplugging or disabling the MAF and see if the trims settle some. I had 25% trims on a 408 and it turned out to be the MAF being bad.

Sean Collins

First check the grounds on the back of the cylinder heads. you have a loose one looking at those codes.
Fuel trims being pegged could be from bad sensor grounds.

wheeljo2

iTrader: (2)

Thanks for the advice Sean. I did notice a ground wire loop on the driver's side harness that includes the fuel injector sensors alternator connections up to the IAT and MAF. You may be on to something here. I did hook it up but believe it was sandwiched in betweent the bolt and tube bracket that connects to the header pipes. Let me disconnect the bracket and bolt the ground wire directly to the head itself and see if it makes a difference. No ground strap bolted to the passenger side however, should there be??

wheeljo2

iTrader: (2)

Thanks Rhino79, I just bought a scanner so let me try what you recommend and see if I can check the trims with and without the MAF hooked up and I'll report back.

wheeljo2

iTrader: (2)

Located the driver's side sensor ground and tightened it up (could have been a bit loose). Do not see a sensor ground on the passenger side head, is there suppose to be one? I reset the codes and drove it, it runs strong and the check engine light did not come on but I still had several of the same codes when I checked the diagnotics.

BLK02WS6

iTrader: (2)

Not one on the passenger side. But there are three ground wires (two connectors - two wires into one of them) on the drivers side. Make sure you have them all. Also check all of your fuses - there is one for the sensors that may be blown.

wheeljo2

iTrader: (2)

The one ground with two wires is secured. The other ground I see is a ground strap on the chassis to the block. Is that the other one you are talking about? Will also check the fuses as you recommend, don't recall seeing a sensor fuse is it in the box next to the battery? Do you happen to know what the number is? Thanks again.

BLK02WS6

iTrader: (2)

What car is it - F-Body?? If so,

There should be another one on the back of the DS head - black wire.

I think that fuse is in the box on the side of the dash. (not near a car to check).

wheeljo2

iTrader: (2)

I'm sorry it is a 99 corvette and both grounds (3 wires) are on the DS, none on the PS that I have found.

Sean Collins

There is a ground by the starter on the Bellhousing bolts that could be loose and cuasing havoc. Passenger side.

wheeljo2

iTrader: (2)

Thanks Sean, I'll check for that. I did replace the starter recently but do not remember seeing a ground in the area. Is the wire coming off the wiring harness itself? You are not talking about the bracket that supports the harness are you?

BLK02WS6

iTrader: (2)

Yeh, the vettes have different grounds than the F-Bodies - and they are known to cause problems. Do some searching around - there was a diagram showing where they all are somewhere awhile back. They may need to be cleaned up to ensure good contact. Chased gremlins on one for weeks and it turned out to be a ground - while logging, all of the sensors would suddenly go bizerk and the car would stall out.

98Z28CobraKiller

iTrader: (17)

Yeah I read a write up that some guy did over on the corvette forum that showed all of the ground points. I believe that the vette has a ground bolt that holds a connector with female ends that is located towards the front of the chassis by the radiator (it mates to a male plug that can be removed without having to unbolt it). It is low on the frame and the contacts get corroded.