Pinpoint Test C : DTC (Diagnostic Trouble Code) P1780
- C1 KOER (KEY ON, ENGINE RUNNING) SELF-TEST
- Using a diagnostic scan tool, perform a KOER self-test.
Is the DTC P1780 set?
Yes GO to C2 No No trouble found with the Tow/Haul system. If the Tow/Haul lamp does not illuminate, REFER to: Instrument Panel And Interior Switches Illumination . - C2 CHECK FOR POWER AT TOW HAUL SWITCH
- Ignition OFF.
- Disconnect Selector Lever Assembly C2810 .
- Ignition ON.
- Measure:
Positive Lead Measurement / Action Negative Lead C2810-2 Ground
Is the voltage 11 volts or greater?
Yes GO to C3 No VERIFY the AJB fuse 31 (10A) is OK. If OK, REPAIR circuit CB131 (BU/OG) for an open. If not OK, REFER to the OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short. - C3 CHECK GROUND CIRCUIT TO PCM/TCM
- Ignition ON.
- Measure:
Positive Lead Measurement / Action Negative Lead C2810-3 Ground
Is the resistance less than 3 ohms?
Yes INSTALL a new tow/haul switch. Refer to: Selector Lever Knob . No GO to C4 - C4 TEST THE GROUND CIRCUIT FOR AN OPEN
- Disconnect If equipped with 3.2L diesel, TCM C1750 .
- Disconnect If equipped with 3.5L engine, PCM C1551B .
- Disconnect If equipped with 3.7L engine, PCM C175E .
- If equipped with 3.2L diesel, measure:
Positive Lead Measurement / Action Negative Lead C2810-3 C1750-53
- If equipped with 3.5L engine, measure:
Positive Lead Measurement / Action Negative Lead C2810-3 C1551B-90
- If equipped with 3.7L engine, measure:
Positive Lead Measurement / Action Negative Lead C2810-3 C175E-93
Is the resistance less than 3 ohms?
Yes INSTALL a new PCM/ TCM. For the 3.2L diesel, REFER to: Transmission Control Module (TCM) - 3.2L Duratorq-TDCi (148kW/200PS) - Puma . For the 3.5L or 3.7L engine, REFER to: Powertrain Control Module (PCM) - 3.5L . Refer to: Powertrain Control Module (PCM) - 3.7L . PERFORM the Transmission Strategy Download procedure. REFER to: Transmission Strategy Download . No REPAIR the circuit.