I have a TPi set up on an older car using a Street & Performance stand alone harness made for use with a 730 ECM and I have problems! As soon as the key is turned to the "on" position the check engine light comes on and never shuts off even after the engine is started. It also will not give any codes at all and will not communicate with a scan tool. It is running in limp mode or fail safe mode becsue it is not using the chip at all. WHat conditions cause the 730 ECM to go into limp mode or fail safe mode? I know its not the ECM itself beacuse I have swapped that with a known good one. I also replaced the ignition module and checked the pickup coil to ensure it had the proper resistance. I have unplugged all of the sensors just to make sure that none of them are grounded but still the same thing. I feel it has a pretty serious fault becasue the check engine light comes on instantly as soon as you turn the key, so that makes me feel it is more than a wrong reading. Any help would be apreciated. Thanks Steve

 

Hmmmm....well, if it runs at all then at least we know the ecm is pulsing the injectors and therefore working. I'm also assuming that you get the 1 or 2 second fuel pump shot at first. The check engine light should come on with the key (before it starts) so that part is normal also. I'd start by troubleshooting the problem with the scan tool not working. Possibly there is a problem in the wiring between the ecm and the ALDL connector? Don't know what scan tool you are using but can its settings be messing you up? You definitely need to know what trouble codes you have to go further, I'd say.

Another way to retrieve your trouble codes is to jumper terminals A and B on your ALDL and get the codes by watching your check engine light flash. A good explanation of this procedure is shown here:

http://chevythunder.com/fuel%20injec...g%20pg%20A.htm

Have at it, and good luck

Steve

 

Well, now I went back and read your other posting and it sounded like you tried diagnostic mode and got nothing from the check engine light. If that is the case, it clearly points to a problem in your wiring harness. Either it is not going into diagnostic mode when you jumper the ALDL terminals, indicating a problem in the wiring between the ALDL and the ecm, or there is a short in the check engine wire between the light and the ecm. That will cause it to stay on all the time.

Gotta get those codes!

Steve

 

You could also have a problem with the PROM or chip itself. When you turn the key on, the SES light should blink once and then stay on. If it doesnt blink, then the problem is the PROM or the ECM.