Well gang...
Mopar1973Man is back out in his shop and found the cause of P1689 error codes.
Quote:
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P1689 - No Communication Between ECM and Injection Pump Module Data link circuit failure between ECM and fuel injection pump. Low power, engine derated, or engine stops.
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A lot of us assume its the injection pump that causes this which in most cases could be. But I was doing a fuel pressure test (cranking). This requires to pull the fuel system relay out of the PDC box under the hood...
Lower left side labeled fuel pump...
When this relay is missing the VP44 doesn't energize nor pump fuel. It allows you to do the cranking test. But it also sets a P1689 and CEL light. So for all of you that have a P1689 error code present check your fuel pump relay first by trading with another relay!
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Michael Nelson - 2002 Dodge Cummins
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