I have been having TPS issues with my car so we hooked up a scan tool but it never gets a signal from the ECM. What would cause this. We have tried two different scanners and the ECM is a brand new AC delco. thanks in advance.

any ideas anyone?

You did say anyone, so its your own fault

How does it run?

I ended up in similar situations but it was running funky, ECM would give no codes by flashing SES light or with ALDL on my laptop.

Ended up being a bad ECM the sensus was, when ya can't get any codes anymore and it runs bad......

New ECM fixed that but now I got chip problems.

Wanted Prom & memcal for 86 2.8 T5 MPFI 7032 ECM

The idle kinda searches around 800-1500 and sometimes stays at 1500. I can get codes to come up with the aldl through the SES light but the scanner won't even communicate with the ECM.

i had that problem. i was using a snap on scanner and it wouldnt do anything. luckily i work at a gm dealer and i used a tech 1 and it communicated no problem. though you could check your pins in your aldl and your scanner to ensure contact. you can teat and adjust your tps with a volt meter if you have no luck with a scanner. it should be at .5 volts closed throttle and 5 volts at wot. doesnt have to be exact

we tried a tech1 and tech2 scanner and neither worked. I have adjusted the TPS with a volt meter multiple times. the volt changes randomly like there is a short in the wire somewhere. not sure why the scanners won't work though.

i had a buick park ave that did that. i would adjust the tps, tighten the screws, then bump the throttle and it would be all messed up. it ended up being the tps bad. that communication prob. does sound goofy though, you could check to make sure you at least have a power or ground in the terminals of your aldl. the two pins may be ok to flash the light but you may have a broken wire or blown fuse to power up a scanner in another pin

If you are using a scanner that is only for OBD-II ecm's then it will not scan. All third gens didn't have this computer since it was around 96 when they came out. So that should solve you issue with the scanner.

no it shouldn't since a tech 1 is an obd 1 scanner and a tech 2 will still do obd 1 functions.

what wires should i check that go from ecm to aldl?

I will ask does your cigarette lighter work? Is that fuse blown?
I know on the GM trucks if the cig fuse is blown or the socket
is bad a scanner will not/cannot communicate with the PCM.

yes it does work and there are no blown fuses. thanks any other ideas?

Gotta chime in on this, I am having a similar problem, cannot get my ecm to respond to an AutoXray with the ODB1 connector.

OK so i found the wire diagram for the ecm and there is a orange and a blac/white that go from aldl to the ECM. The orange wire has continuity from aldl to ECM but the black/white wire does not. any ideas?

The black with white stripe wire goes to ground. Usually tied under the dash. This is from pin A of the ALDL connector.

RBob.

yes but it goes from pin A to the ECM. it's only a ground for the ECM?

Rob, just tried using a Max 232 aldl cable this time as opposed to the two transistor circuit. Still cannot communicate with my ecm. Like i said , i tried Datamaster, efi live, tunerpro, Freescan. I turn the key to the on position and do not get an SES light blink, I just turn the key on and always get a solid light. Any ideas?

Ok, I am getting a blink now when i turn the key. Still no connection through my laptop though.

UPDATE! It was a bad ecm not giving me 5v out of pin M on ALDL.