I posted this question in the ratty 86 thread but am in need of a quick answer. How does the under panel onthe passenger side come off so I can get to the ECM bracket and pull down the ECM?

I am tryng to get this beast to run so my brother in law won't part it out.

 

The lowest plastic panel (where the courtesy light is imbedded) comes off with phillips screws. Unplug the light.

Look up and you'll see the ECM "retainer" nearer the middle of the car. On either side, you'll see the head of two 10mm bolts. Remove those. The cover will come off and the ECM will drop down. You can completely drop it and unplug/swap it -- if necessary.

Or chip it and reprogram.

Are you assuming bad ECM from ALDL codes?

 

Thanks, I guess I need to get myself up side down in there tomorrow to locate the screws. I coudn't feel any kneeling beside the car today.

I get no check engine light so I can't get any codes. The lamp in the Check Engine Light is good and the fuses for the ECM and the Check Engine Light both have 12V+ with the ignition on, but there's still no check engine light with the ignition, on so I assumed it is not being grounded through the ECM. I've had to clean the ECM contacts on several of my Jaguars when things got wierd so I am hoping it could be a bad contact at the Vette's ECM that's the reason the check engine light does not come on with the ignition on and the starter does not crank. Either that or a bad ECM. I Have no prior history with this car, but the wiring has been really screwed up by someone looking for a nonstart problem.

 

I know the kneeling is a pain, I just replaced the heater core in my 85. I cound not physically lay on my back to do the work. I used a garden knee pad and a heavy duty moving pad to cushion my sorta bad knees. I scrounged up a magnifying mirror to get all the stuff out. To remove the ECM is pretty easy, just be careful not to bend the pins. Bud Lite will ease the pain after.

 

My panel is held by a couple of 7mm screws in the rear edge (closest to you). There was one more place for a screw, but it was never there.

It looks like there might be provision for some kind of screw or stud or something at the very front of the panel (like on the driver's side), but my car does not have anything there.

 

Three screws, beside light and 2 to the right of light.
Stud with speed nut or screw, middle of panel, near firewall.

 

Thanks,

Before I go kneel in the snow with a mirror, this car has carpeting on the under panel that looks worn and threadbare. Is that normal or might someone have glued carpet over the screws? I couldn't feel any screws underneath but I could see a screw on the outside edge of the panel near the fuse block; the panel could be pulled down a bit at that point so that screw was not holding it up.

 

There are no screws in carpet area, all forward of carpet.

 

Panel removed, you can see the 2 big bundle of wires going up to ECM.

 

there is an E-type jag sitting in a back yard near Gas city, Indiana. Been sitting there a few years. Looks forlorn.

 

Thanks again, Dan, A picture IS worth a lot of words.

It looks like the panel removed in your photo is already gone from this car and I was trying to remove the one that curves up to the plastic dash trim; I did see the bundles of wires yesterday that you mention.

So....I need to get my head under there to find the ECM rack mounting bolts. I can't tell from the component location view in 8A, but from ECM pics on eBay I assume they go forward into the firewall. Time for the 1/4" drive ratchet.

Ah, Getting a little closer each day Due to this great site and your experience. Perhaps I can save it yet.

 

ECM removed

 

OK, got it out after I found the second downward facing bolt under the mass of wires. Unpluged the ECM and sprayed contact cleaner on the pins and connectors, but no change in function and no check engine light.

Came inside to find a diagram of the ECM connectors so I can check voltages at the pins you suggested and will be checking to see if the loose orange wire pulled from the harness on the left side goes to the fuel pump relay or perhaps to the junction of fuseable link H.

Thanks again.

 

The orange wire hanging out of the harness on the left side had continuity to B1 and C16 at the back of the ECM plugs and to B1 at the pin side, but I didn't get continuity at the pin side of C16. I connected the orange wire and the fan relay red wire (through an external 30A fuse) to the battery + cable and re-plugged the ECM connections and reconnected the battery. Now when I turn the ignition on I hear a click from the back of the car (doesn't sound like the fuel pump - just a click) but still no check engine light.

I'll pull the ECM plugs again to see if the problem could be in the C16 wire at the plug. Is it best to disconnect the battery to unplug the ECM, or does it matter if it is hot when unplugged?

 

According to Ludis Langen's ECM schematic B1 and C16 are connected together inside the ECM. I verifies that those pins are in fact connected together.

A click from the back could be the power antenna relay.

 

You may want to have a look for the small red wire that powers ECM. Should be somewhere down there, beside battery.

 

Thanks, Dan, I'll look again for the small red wire.

However, with the battery disconnected the orange wire did have a no resistance connection to B1 and C16 at the disconnected ECM plugs, and with the orange wire connected to battery + there was a constant 12V+ between both of them and ground, which I assumed from the wiring diagrams could enable ECM operation, and both of these pins are fed by orange wires. (At first I didn't get voltage at the pin side of C16, but then using a thinner probe that would go farther into the plug I did). I wonder if this orange wire came from the oil pressure switch as I think you suggested before and if the oil pressure switch may now be disconnected.

I'll try to get a photo of the revised wiring today with the short red wire extended, the fan relay back in its intended location, and the fan relay's red wire with fuse holder and the orange wire temporarily connected to the battery wire with a large wire nut. It may be a good idea to pull the battery again and clean all the fuseable link connections at the jump start junction block (did GM really expect you to get a jumper cable back there?)

Cliff said these pins are connected inside the ECM, but they were both also getting 12V+ at the plug when not connected to the ECM. One of the RPO codes says this car has a manual antenna and the radio is long gone, but considering the way this car has been manhandled it could be an antenna relay as suggested. Too bad my arms are not long enough to turn the Ign on while listening from the back hatch. Guess I need to find the fuel pump and see if it works wired directly or if it might be the click.

Dan, I may have erred in asking about ECM removal in a new thread because your advice is being split between two threads now. Should I also post this back in the ratty 86 thread and continue there or continue here? I posted a question about the center panel connector there yesterday.