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Ok so I got this Sentra towed in no start car turns over and sometimes starts for a sec. then turns off. I pull codes and can't communicate with the ECM all other modules I can. So I'm thinking power and grounds, O and fan's stay on with key on, so I pulled the wire diagram and to my understanding 15,23,32,66 and 93 are power and 107,108,109 and 112 are ground. All checks were done with key on ECM disconnected at all powers I got batt. voltage and at grounds, batt. ground to ECM ground reading on volt meter was 0.03. Question here is did I miss a power or a ground if not what other test should I do before calling the ECM?
Thank you for your help.
When you check the powers and grounds, you mentioned doing it with the ecm disconnected. I would maybe redo those tests with the ecm connected, with the key on and see if they are all still good. I know those connectors suck to work with... You have to take them apart, and backprobe, before reconnecting in some cases.
Also, do you have 5v at any of the easily accessable sensors? MAF is probably the most convenient to access.
Tutti57 I rechecked the power with it plugged in and on line 32 ssoff that goes to the ecm relay pin 7 on the IPDM drops power when plugged in. Is this normal I also don't have 5v ref it's 1.36v. I disconnected the cam, ckp, tps and app and no 5v. Question is because of the line on 32 not having power is it the cause of all this. Thank you for your help
It looks like pin 32 at the ecm is the ecm relay control wire, so when that one should drop down when connected since the relay coil is a load, and the voltage is dropped by the ecm providing the ground to it.
The only other things I'll add before replacing the ecm is that the 5v ref could be shorted to ground, or another sensor on the 5v could be shorted. MAF, evap pressure, ac pressure are the only others I can think of. Temp sensors don't impact the 5v circuit, so you can skip those.
