Alright, i got a problem truck at the shop and need some fresh views.
07 lmm came in with a no crank no start. Battery’s test good on both digital and with old school analog. Plugged in scanner and no communication. Ohmed 6 and 14, had 60ohms. Had 2.3 and 2.7 volts on same lines. Did power and ground test on ecm and found pin 76 had no power. Continuity test was good back to the fuse block. Found fuse that supplies 76 had 4.5v. Basically relay “pwr/trn” relay was not sending full voltage and swapping relays made no difference. Load testing both the fuse block and pin 76 wire showed no issues so we turned to a ground issue. All grounds tested good though. Put a ground on the ecm and boom, fires up, get ecm comm but we have a p0090 and p2510 code. Plus says 7 of 8 glow plugs are dead.
Now regardless of the ground on the ecm, we find no power on the 12v power to the fpr and turbo solenoid. No output at the ecm. Fpr and turbo wire all load test fine. We check the ground on the fpr wire for resistance and its at 11 ohms. Clean the ground wire at the block and verify engine bulk head connectors are good and we get resistance down to under an ohm from ground on connector back to battery. Put a good used ecm in, flash it, no crank no stsrt is back after 3 times trying to start. 4 time, starts up. Regulator sometimes works, sometimes goes wide open. Same with turbo solenoid. When they dont work, same issue of no voltage for fpr or solenoid.
We have combed the harness looking for issues. None to be found. Im really leading towards a ground issue. Jumping can bus wires makes no difference (really shouldnt since resistance and voltage is in spec). I may have missed some other tests weve done.
Thoughts? According to the customer, this came out of the blue. Hes not done a thing to it before or after this
07 lmm came in with a no crank no start. Battery’s test good on both digital and with old school analog. Plugged in scanner and no communication. Ohmed 6 and 14, had 60ohms. Had 2.3 and 2.7 volts on same lines. Did power and ground test on ecm and found pin 76 had no power. Continuity test was good back to the fuse block. Found fuse that supplies 76 had 4.5v. Basically relay “pwr/trn” relay was not sending full voltage and swapping relays made no difference. Load testing both the fuse block and pin 76 wire showed no issues so we turned to a ground issue. All grounds tested good though. Put a ground on the ecm and boom, fires up, get ecm comm but we have a p0090 and p2510 code. Plus says 7 of 8 glow plugs are dead.
Now regardless of the ground on the ecm, we find no power on the 12v power to the fpr and turbo solenoid. No output at the ecm. Fpr and turbo wire all load test fine. We check the ground on the fpr wire for resistance and its at 11 ohms. Clean the ground wire at the block and verify engine bulk head connectors are good and we get resistance down to under an ohm from ground on connector back to battery. Put a good used ecm in, flash it, no crank no stsrt is back after 3 times trying to start. 4 time, starts up. Regulator sometimes works, sometimes goes wide open. Same with turbo solenoid. When they dont work, same issue of no voltage for fpr or solenoid.
We have combed the harness looking for issues. None to be found. Im really leading towards a ground issue. Jumping can bus wires makes no difference (really shouldnt since resistance and voltage is in spec). I may have missed some other tests weve done.
Thoughts? According to the customer, this came out of the blue. Hes not done a thing to it before or after this
.