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Ok, you may have a short in the engine harness, or a failing ECM. Have the code cleared, and then drive it, let it stumble, and recheck the code. Let me know if the P1652 returns.
Let me know,
Symptom:P1652-J1850 SHORT TO GROUNDWhen Monitored and Set Condition:P1652-J1850 SHORT TO GROUNDWhen Monitored: While the ignition is on.Set Condition: The ECM detects a short to ground on the J1850.POSSIBLE CAUSESECMJ1850 SHORTEDCOMMUNICATIONTEST ACTION APPLICABILITY1 Turn the ignition off.Disconnect the ECM harness connectors.NOTE: Check connectors - Clean/repair as necessary.Measure the resistance between the J1850 circuit in the ECM harness connector andbattery negative.Is the resistance less than 10 Ohms?ENGINE- 5.9LCUMMINS 24VDIESELYes ! Go To 2No ! Replace the ECM.2 Measure the resistance between the J1850 circuit and all other circuits in both ECMconnectors.Is the resistance greater than 100k ohms?ENGINE- 5.9LCUMMINS 24VDIESELYes ! Refer to the Body Diagnostic book Communications section.No ! Repair J1850 shorted to another circuit.