Hi...

My Brother and I recently put an LS376/480 495HP LS3 with a T56 in an 81 Chevy C10. We are dealing with several issues with it running and would like to rule out a bad ECM. We used the GM Connect and Cruise wiring harness and it came with an E67 ECM, GM 19354331. GM wants $710 for this computer but I also have access to EFI Live. Can anyone recommend where to buy a replacement? I have the ECM VIN number, operating system info, etc.

Any help would be appreciated!

Tom

 

You can probably buy a used ECM on ebay from a vendor who will flash your VIN into the unit.

Why not tell us what issues you are having. Have you logged all the important sensors in your EFI Live?

 

If you want it to 100% match, buy another GMPP computer directly from GM. You can't MDI it without a VIN (and using the identifier that it comes with doesn't work in my experience but maybe they've fixed that over the years), and using something like HP Tuners/EFILive to read out your old one and flash your new one isn't going to flash the TAC module portion of that ECM to make sure it's 100% identical.

That being said, what makes you think the computer is bad? They rarely have problems unless something was hooked up incorrectly and you applied power to something you shouldn't have....

 

If you send the me the ecm and if it powers up and I can read it, I can clone it to a used ECM.

 

Here is the back story and the issues we are having...My Brother and I recently installed an LS376/480 495HP LS3 and T56 Super Magnum in his 1981 Chevy C10 stepside. This has been a 4 plus year ground up restoration project.

We purchased the engine, harness, computer and transmission as a package from Pace Performance. The motor and controller are GM’s Connect and Cruise and we followed their instructions (GM 19417417).

- The engine is GM 19432415.
- The harness and controller is GM 19354330 and comes with an E67 computer, GM 19354331.
- The E67 has operating system 12638778 and the vin number shows it is revision 8.
- The fuel system consists of a Walbro 255LPH in tank pump and we used a Corvette filter / regulator, Napa/Wix FIL 3737.
- The fuel pressure is a consistent 58psi. The original off brand filter we used was providing 75psi so we replaced it.
- The exhaust consists of Hooker 2.5” cast iron manifolds, Hooker downpipes with the O2 bungs, 2.5” x pipe and Borla Pro XS mufflers with 2.5” tailpipes out to under the rear bumper.
- The cooling system consists of a Camaro water pump (to match the mid 2000’s truck brackets we used), a CU730 radiator (for a 454) and a pair of 12” Spal electric fans.
- The relays with the GM connect and cruise control the fuel pump as well as the cooling fans.
- The throttle body has the gold blade (included with the kit).
- The throttle pedal is the Cadillac CTSV one (included with the kit).
- The air intake system consists of a factory air filter box from a mid 2000’s Chevy truck, a new Wix air filter, 4” aluminum tubing to the throttle body with (1) 45 deg bend at the throttle body.
- The MAF sensor, GM 15865791, is mounted 11” from the throttle body, 6” from the air filter, and is in the middle of a 12”+ straight section of tubing.
- The battery is grounded to the engine block and truck frame, the grounds from the GM harness are connected to the heads and the frame of the truck is grounded to the cab.
- There does not appear to be any voltage issues at the GM fuse block and all of the fuses are good. The voltage is a consisted 13.44V or so when the truck is running

We originally started the engine in late December of last year. It fired right up and it idled fine. We moved it in and out of the garage a few times but did not drive the truck anywhere. We just received the rear fenders from the body shop and installed them so we were able to take it for a ride. The first thing we noticed was that there was substantial bucking in 1st gear just cruising around the neighborhood in at 20mph or so. The next time we started it, the throttle pedal was extremely lazy and felt like a dead pedal. We were able to take it for a ride but after 5 minutes of cruising around 35mph or so, the engine seemed to die and again it had a dead throttle pedal. It was still running but it wouldn’t get out of its own way. After disconnecting the battery for 10 seconds, we were able to restart it and drive it home. On the next trip it did the same thing but this time we disconnected the MAF sensor. The idle picked up and again we were able to drive it home. After disconnecting the battery again, the exact same thing happened, but this time it finally threw some codes...

These were the Confirmed Codes:

P0102 Mass or Volume Air Flow Sensor ‘A’ Circuit Low
P0131 O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
P0112 Intake Air Temperature Sensor 1 Circuit High Bank 1
P0151 O2 Sensor Circuit Low Voltage Bank 2 Sensor 1

It also had the (4) exact same pending codes but added this one as well:

P0506 Idle Control System RPM – Lower Than Expected

At that time I changed the MAF and used a Hitachi MAF0034. I cleared the codes, went for another ride and the same thing happened. I was using Blue Driver to take some log data, and it appears that the O2 sensors were very lean. And when the issue happens, they go to .005V. Once the MAF is unplugged, both of them jump up to .950V or so. The O2’s read very low voltages at idle but its extremely rich, to where your eyes water. I was thinking there may be an issue with a corrupted tune, so using EFI Live, we replaced the original tune with Revision 7. Last night we drove the truck for about 10 minutes and it seemed to work well and had tremendous power. We ran out of time for the night so I’m still skeptical the tune fixed it. Hopefully we can do another road test tonight.

I did reach out to an ECM supplier and they won’t sell you an ECM without a vehicle VIN number. And GM wants $707 for a new one. I did call GMPP, and they recommended I try to find a dealer that will diagnosis it. They did give me a case number but would rather try to figure this out on our own.

Any input would be appreciated!

Tom

 

 

It sounds like you have more of a tuning issue than bad ecm issue. Id recommend tuning it anyways, I have yet to see a GMPP tune that was great. I have another on at the shop right now to get re-tuned.

 

In my experience, Despite the directions they give and the recommendations they make, The tune is always off on those. I have worked on 3 of those and every one needed tweaking buy a professional tuner.

Also had my share of issues with the harnesses not being correct either.

 

Quick update:

We found a poor splice in the fuse box and fixed it. We took the truck for a ride, and again around 80 seconds the truck went in to limp mode (no throttle response). At that time it threw two codes, P0102 and P0113 which are both related to the MAF. We unplugged the MAF in order to drive the truck home.

We understand a vacuum leak will look like a bad MAF, so we checked the intake manifold bolts and several of them were loose. So we torqued them to 44 inch pounds and then 89 inch pounds.

We reset the check engine light, went for another ride and the truck died again around 80 seconds. This time it threw 5 codes, P0102, P0113, P0131, P0151, and P0506.




Below are some graphs from EFILive.

Around frame 3200 it goes into limp mode:


Around frame 5589 we disconnected the MAF to get home:

 

I have installed several of these systems in customer vehicles. Just as installing a CAI on X chevy truck corvette etc always requires MAF tuning to get the MAF correct and then tweak the tune accordingly after that for driveability and power after the upgrade.

Save yourself the time money and headache load it up take it to a pro tuner in your area let them strap it down and see what it does. Guarantee you it's tune that needs to be tweaked to fit your application..