Fuel Pump Electrical Circuit Diagnosis (K07UFM)
Fuel Pump Electrical Circuit Diagnosis (LC8\K07\UFM)
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.
Circuit/System Description
The engine control module (ECM) enables the fuel pump relay when the ignition switch is turned ON. The ECM will disable the fuel pump relay within 30 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The ECM disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.
Diagnostic Aids
The following conditions may cause the fuel pump fuse to open:
* The fuse is faulty.
* There is an intermittent short to ground in the supply voltage circuit of the liquid propane control module.
* The LPG Control Module, LPG fuel pump, or the LPG cut-off solenoid valve has an intermittent internal condition.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
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
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
J 43244 - Relay Puller Pliers
Circuit/System Verification
Note: An open or a short to voltage in the control circuit will cause both the Ckt. Open Test Status and the Ckt. Short Volts Test Status parameters to display Fault.
1. Ignition OFF.
2. Verify the fuel pump is not activated
• If the fuel pump is activated
Refer to Circuit/System Testing
• If the fuel pump is not activated
3. Ignition ON.
4. Verify the fuel pump and LPG cut-off solenoid valve activate when commanding the fuel pump relay ON and OFF with a scan tool.
• If the fuel pump or LPG cut-off solenoid valve does not activate
Refer to Circuit/System Testing
• If the fuel pump and LPG cut-off solenoid valve activate
5. All OK
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down. Disconnect the KR23A fuel pump relay.
2. Verify the fuel pump is OFF.
• If the fuel pump is ON
Repair the short to voltage on the fuel pump relay component control circuit.
• If the fuel pump is OFF
3. Test for less than 10 ohms between the fuel pump relay ground circuit and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms , repair the open/high resistance in the ground connection.
• If less than 10 ohms
4. Ignition ON.
5. Verify a test lamp illuminates between the fuel pump relay B+ circuit and ground.
• If the test lamp does not illuminate
1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms of greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is OK and there is voltage at the fuse.
• If the test lamp illuminates
6. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the LPG cut-off solenoid valve. It may take up to 2 minutes for all vehicle systems to power down.
7. Test for less than 10 ohms between the LPG cut-off solenoid valve ground circuit terminal B and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms of greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
8. Disconnect the in-line harness connector at the LPG fuel pump.
9. Test for less than 10 ohms between the LPG fuel pump ground circuit terminal B and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms of greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
10. Connect the harness connectors for the LPG cut-off solenoid valve and fuel pump.
11. Ignition ON, connect a 30 A fused jumper wire between the fuel pump relay B+ circuit and the component control circuit.
12. Verify the LPG cut-off solenoid valve and fuel pump are activated.
• If the LPG cut-off solenoid valve and fuel pump do not activate and the circuit fuse is good
Repair the open/high resistance in the component control circuit.
• If the LPG cut-off solenoid valve and fuel pump do not activate and the circuit fuse is open
1. Ignition OFF
2. Disconnect the following components
* LPG cut-off solenoid valve
* LPG fuel pump
* Liquid propane control module
3. Test for infinite resistance between the component control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, test the following components for excessive current draw and replace as necessary.
* LPG cut-off solenoid valve
* LPG fuel pump
* Liquid propane control module
• If the LPG cut-off solenoid valve does not activate
1. Disconnect the harness connector at the LPG cut-off solenoid, Ignition ON.
2. Verify a test lamp illuminates between the LPG cut-off solenoid valve control circuit and ground.
• If the test lamp does not illuminate, repair the open/high resistance in the circuit.
• If the test lamp illuminates, test or replace the LPG cut-off solenoid valve.
• If the fuel pump does not activate
1. Disconnect the in-line harness connector at the LPG fuel pump, Ignition ON.
2. Verify a test lamp illuminates between the LPG fuel pump control circuit and ground.
• If the test lamp does not illuminate, repair the open/high resistance in the circuit.
• If the test lamp illuminates, test or replace the LPG fuel pump.
• If the LPG cut-off solenoid valve and fuel pump activate
13. Test or replace the KR23A fuel pump relay.
Component Testing
1. Ignition OFF, disconnect the KR23A fuel pump relay.
2. Test for 70-110 ohms between terminal 85 and 86.
• If not within the specified range
Replace the KR23A fuel pump relay.
• If between 70-110 ohms
3. Test for infinite resistance between the terminals listed below:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than infinite resistance
Replace the relay
• If infinite resistance
4. Connect a 3 A fused jumper wire between relay terminal 86 and B+. Connect a jumper wire between relay terminal 85 and ground. Test for less than 2 ohms between terminals 30 and 87.
• If 2 ohms of greater
Replace the relay
• If less than 2 ohms
5. All OK
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)
* Control Module References Control Module References for ECM replacement, programming, and setup