DTC P0628, P0629, or P12A6
Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5495422 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0628 Fuel Pump Control Circuit Low DTC P0629 Fuel Pump Control Circuit High DTC P12A6 Fuel Pump Power Control Module Enable Circuit Performance Diagnostic Fault Information
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performanc |
|---|---|---|---|---|
| Control | P0628, P12A6 | P12A6 | P0629, P12A6 | P12A6 |
Typical Scan Tool Data Fuel Pump Control Circuit High Test Status
| Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
| Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay | |||
| Control | Not Run / Okay | Not Run / Okay | Malfunction |
Fuel Pump Control Circuit Low Test Status
| Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
| Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay | |||
| Control | Malfunction | Not Run / Okay | Not Run / Okay |
Fuel Pump Control Circuit Open Test Status
| Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
| Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay | |||
| Control | Not Run / Okay | Malfunction | Not Run / Okay |
Circuit/System Description For an overview of the component/system, refer to: Fuel System Description
| Circuit | Description |
|---|---|
| Control | The output circuit is switched to 12 V to activate the component. |
| Component | Description |
|---|---|
| K20 Engine Control Module | The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly. |
| K111 Fuel Pump Power Control Module | The control module contains a microprocessor used to process input data to control outputs. The control module communicates with the control module K20 via serial data. |
When the ignition is turned On, the ECM sends a 12 V signal to the control module K111 to enable the fuel pump. If the engine is not started, the control module K111 turns the fuel pump Off after 6 s. Conditions for Running the DTC P0628 DTC U18A2 = Not set Engine Speed = Greater than 0 RPM Ignition and Start Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met P0629 DTC U18A2 = Not set Engine = Cranking Greater than 0 RPM Ignition and Start Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met P12A6 DTC P11FF, U18A2 = Not set Engine Speed = Cranking /Running — For less than 1 s Ignition and Start Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC Control Circuit = Commanded state does not match the actual state — For greater than 2 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification
- Ignition » On / Vehicle » In Service Mode
- Verify the scan tool parameter: Fuel Pump Control Circuit High Test Status = Not Run or Okay Fuel Pump Control Circuit Low Test Status = Not Run or Okay Fuel Pump Control Circuit Open Test Status = Not Run or Okay ⇒ If not the specified state Refer to: Circuit/System Testing ⇓ If the specified state
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
- Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC is not set
- All OK. Circuit/System Testing
- Ignition/Vehicle & All vehicle systems » Off
- Disconnect the electrical connector: K111 Fuel Pump Power Control Module
- Ignition » On / Vehicle » In Service Mode
- Perform the scan tool control function: Fuel Pump » Off Verify a test lamp does not turn On between the test points: Control circuit terminal 18 & Ground ⇒ If the test lamp turns On 4.1. Ignition/Vehicle » Off & Remove » Test lamp 4.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 4.3. Ignition » On / Vehicle » In Service Mode 4.4. Test for less than 1 V between the test points: Control circuit terminal 18 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇒ If less than 1 V » Replace the component: K20 Engine Control Module ⇓ If the test lamp does not turn On
- Remove » Test Lamp
- Perform the scan tool control function: Fuel Pump » On Verify the scan tool parameter: Fuel Pump Control Circuit Low Test Status = Okay ⇒ If not the specified state 6.1. Ignition/Vehicle » Off 6.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 6.3. Test for infinite resistance between the test points: Control circuit terminal 18 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇒ If infinite resistance » Replace the component: K20 Engine Control Module ⇓ If the specified state
- Connect a 3 A fused jumper wire between the test points: Control circuit terminal 18 & Ground
- Perform the scan tool control function: Fuel Pump » On Verify the scan tool parameter: Fuel Pump Control Circuit Low Test Status = Malfunction ⇒ If not the specified state 8.1. Ignition/Vehicle » Off & Remove » Jumper wire(s) 8.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 8.3. Test for less than 2 Ω between the test points: Control circuit terminal 18 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If the specified state
- Test or replace the component: K111 Fuel Pump Power Control Module Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification For control module replacement, programming, and setup refer to: Control Module References