1993 Cummins N14 ECM issues - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 2 (permalink) Old 10-25-2019, 10:05 PM Thread Starter
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1993 Cummins N14 ECM issues

HI. This is my first post in this forum so please forgive any screw ups on my part.
Full disclosure: I am not a qualified Cummins diesel mechanic but I have been given the task of maintaining my employer's 1993 Freightliner dump truck. [I work for an equipment rental company/contractor]

Now on to the meat of the matter. The engine is an N14 that seems to run well. But in recent months it has seen fit to derate itself with a yellow and flashing red light on the dash. Quckserv on the Cummins web site has been most helpful. The trouble codes are 123, 141, 145, 154, 213, 352, 415 and 422. Everything seems to relate to code 352, low voltage [0.5 volts] at pins 2,3,5,12,21 and 22 of the sensor harness. Pin 10 of the OEM harness, however, does have 4.5 - 5.0 volts. At all connectors at the sensors I am getting 0.3 to 0.6 volts. As for code 422, coolant level sensor, there is no such sensor on this truck. After unplugging all sensors and the shorting plug at the coolant level sensor plug I still get the 352 code and still only get low voltage. It's looking a lot like the 5 volt supply to the sensor harness is dead. My big question is, can I tap off of the 5 volt supply coming from pin 10 of the OEM harness or can I add on an external 5 volt source to the 5 volt circuit in the sensor harness? Tight budgets preclude taking the truck to the Cummins distributor for a proper check over.

Thankyou in advance for ANY advice!!!
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post #2 of 2 (permalink) Old 10-31-2019, 11:35 PM
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I would verify that I have good oil pressure since you have code 415. I would also disconnect the sensor harness from the ecm and check for the 5 volt supply wires being shorted to ground with and without the sensors connected using a dvom. If the wiring tests ok I would want to connect a test ecm to see if the problem goes away. Having access to quickserve should point you to the solution. I would not try to tap into or add any other 5 volt wires.
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