P12B7
DTC P12B3, P12B5, P12B7, P12B9, P12BB, P12BD, P12BF, or P12C1
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P12B3
- Cylinder 1 Injection Timing Retarded
DTC P12B5
- Cylinder 2 Injection Timing Retarded
DTC P12B7
- Cylinder 3 Injection Timing Retarded
DTC P12B9
- Cylinder 4 Injection Timing Retarded
DTC P12BB
- Cylinder 5 Injection Timing Retarded
DTC P12BD
- Cylinder 6 Injection Timing Retarded
DTC P12BF
- Cylinder 7 Injection Timing Retarded
DTC P12C1
- Cylinder 8 Injection Timing Retarded
Circuit/System Description
The engine control module (ECM) has the ability to learn injector timing performance. With the engine at operating temperature and in closed throttle decel mode, the ECM will pulse each injector individually and measure the changes in rotational speed of the crankshaft using the input from the crankshaft position sensor (CPS). The ECM will run this diagnostic under three different fuel rail pressures for each injector. The ECM will adjust the timing of fuel delivered by each injector to obtain the desired RPM increase. The ECM stores the injector timing value required to increase the crankshaft speed by the desired RPM. If the ECM cannot control an increase in RPM for a given injector the appropriate code will set for that injector.
Conditions for Running the DTC
* Ambient air temperature is above -5° C (23° F).
* Fuel temperature is between 0-80° C (32-176° F).
* Engine temperature is greater the 50° C (122° F).
* Battery voltages is greater than 10 V.
* Time since last combustion event is between 10-30 s.
* Vehicle is in decel fuel shut off mode.
* Engine speed is between 950-1850 RPM.
* The difference between the Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure is less than 2.2 MPa (320 psi).
* No gear change has occurred.
* Lambda sensors are adapted.
* Vehicle is not in 4WD (if equipped).
* Exhaust brake is not ON (if equipped).
* No other DTCs are present.
* The DTC runs when the above conditions exists.
Conditions for Setting the DTC
Zero fuel correction has reached maximum value for greater than 10 s.
Action Taken When the DTC Sets
DTCs P12B3, P12B5, P12B7, P12B9, P12BB, P12BD, P12BF and P12C1 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P12B3, P12B5, P12B7, P12B9, P12BB, P12BD, P12BF and P12C1 are Type B DTCs.
Diagnostic Aids
* This Diagnostic parameter is stored in the ECM over a period of time. Time to set this DTC may take several drive cycles.
* Contaminated or improper fuel quality may cause this DTC to set.
* Worn base engine components or differences in cylinder compression may cause this DTC to set
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Fuel System Description (Fuel System Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information.
Circuit/System Verification
1. Verify the proper fuel is used. Refer to Fuel System Specifications (Fuel System Specifications) and Contaminants-in-Fuel Diagnosis (Contaminants-in-Fuel Diagnosis).
2. Verify there are no aftermarket performance enhancing devices install on the vehicle.
Circuit/System Testing
Perform a cylinder compression test. Refer to Engine Compression Test (Testing and Inspection).
If the engine compression is within specifications replace the appropriate Q17 fuel injector.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Injector Replacement (Left Side) (Fuel Injector Replacement (Left Side)) Fuel Injector Replacement (Right Side) (Fuel Injector Replacement (Right Side))
* Perform the Fuel Injector Flow Rate Programming (Procedures) procedure after replacement of a fuel injector.
* Control Module References (Programming and Relearning) for ECM replacement, programming, and setup.