Sunday, August 12, 2012

Ford F-350 Super Duty, misfire, code P1273

VEHICLE:  2000 Ford F-350 Super Duty Lariat 7.3L, V8, MFI, OHV, VIN F
MILEAGE:  289,250
Customer Concern: The engine will misfire intermittently and has a code P1273.

1. Clear the codes and perform the injector buzz test to determine if the P1273 will reset.

2. If the code is a hard fault then at the valve cover connector, swap the Brown/Yellow (BN/YE) at pin 4 with the Tan wire at pin 3. Then clear the codes and redo the injector buzz test to see if it returns. If the code changes to a P1271, remove the valve cover and check for a loose Under Valve Cover (UVC) harness, damaged valve cover gasket, or faulty injector.

3. If the code P1273 still sets, put the wires back in their original location at the valve cover connector. Go to the Injector Driver Module (IDM), inside the Left Hand (LH) fender, and swap the BN/YE wire at pin 21 with the Tan wire at pin 6. Again clear codes and redo the injector buzz test. If the P1273 still sets, replace the IDM. If the code changes to a P1271, check for high resistance in the BN/YE wire between the IDM and valve cover connector.

Potential Causes:
Under Valve Cover (UVC) Harness
Valve Cover Gasket
Injector Driver Module (IDM)
Fuel Injector(s)
Fuel Injector Wiring

Confirmed Fix:
Replaced Engine Wiring Harness Connectors: The problem was in the engine harness connector that plugs in to the outside of the valve cover gasket.

Tech Tips:
The cylinder numbering on this Ford F-350 Super Duty Lariat 7.3L  is 1, 3, 5, 7 front to back on the Right Hand (RH) side and 2, 4, 6, 8 front to back on the Left Hand (LH) side.

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