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Hello I am in need of some assistance on a Mercedes diesel. Vehicle came in with multiple issues and customer attempted to repair the issue himself.
Initial customer request was programming fuel injectors that customer replaced to remedy lack of power, Excessive Smoke and Loss of acceleration.
Was able to verify customers concern and found during medium to heavy acceleration instrument cluster would perform bulb check and vehicle acted like the ignition was cycled on-off-on.
reinstalled customers old injectors as a first step due to the injectors not coding properly. During injector replacement found heavily damaged Injector wiring that was shorting out during failure causing all of the injectors to cut off for a couple seconds and then fire again. Still no codes present during or after the failure.
Repaired injector wiring and retested system. Now the issue only happens when it is up to temperature during heavy acceleration.
Used Oscilloscope to test - Throttle Position, Crankshaft Position, Camshaft Position, Injectors, Powers and Grounds for the ECM.
Throttle position sensor didn't have a consistent waveform and would drop off while problem was happening.
CKP is a strong analog waveform that is consistent through the problem.
CMP Is a sharp Hall Effect signal with no drops during Problem. Have battery and ignition voltage at the ECM, Grounds are all minimal resistance and show no issues. During testing found ECM Connector 2 Pin 44 - EC87 Relay circuit which is a 12v PWM circuit is dropping out.
What I am trying to figure out is if the PCM is not capable of closing that circuit or if I am missing something about this circuit. Any help is much appreciated. Sorry about the confusing description.
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