Circuit Description
The fuel pump relay coil is supplied power via the engine controls power relay, switched B+. The engine control module (ECM) controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this diagnostic trouble code (DTC) will set.
When the ECM detects any reference pulses from the crankshaft position (CKP) sensor, the ECM will enable the fuel pump. The relay is used in order to control the high current flow to the fuel pump. This allows the ECM driver to only have to handle the relatively low current used by the relay.
Conditions for Running the DTC
| • | The battery voltage is between 7.5-15 volts. |
| • | Shorts to ground and open circuits are tested only during the power-down phase. |
| • | Shorts to battery voltage are tested continuously. The engine RPM must be more than 40 RPM. |
Conditions for Setting the DTC
A short to ground, an open circuit, or a short to battery voltage detected on the control circuit.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
Check for the following conditions:
| • | Poor connections at the ECM or at the component--Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for the proper procedure. |
| • | Proper operation of all circuits that are spliced to the fuel pump relay B+ circuits |
| • | Damaged harness--Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. |
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for the intermittents.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the relay operates. Repeat the commands as necessary.
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This check can detect a partially shorted coil which would cause an excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open, the amps drop to 0 or short, go to above 0.20 amp.
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Perform the idle learn procedure when replacing the ECM or the throttle body.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||
Does the relay turn ON and OFF? | -- | Go to Step 3 | Go to Step 5 | |||||||||||||
Is the amperage within the specified range? | 100-200 mA | Go to Diagnostic Aids | Go to Step 4 | |||||||||||||
4 |
The DMM should display an infinite resistance. Does the DMM display an infinite resistance? | -- | Go to Step 13 | Go to Step 11 | ||||||||||||
5 |
The test lamp should illuminate. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 12 | ||||||||||||
6 | Using an unpowered test lamp connected to ground, probe the relay control circuit in the fuel pump relay harness connector. The test lamp should NOT illuminate. Is the test lamp OFF? | -- | Go to Step 7 | Go to Step 10 | ||||||||||||
7 | Using an unpowered test lamp connected to battery positive, probe the relay control circuit in the fuel pump relay harness connector. The test lamp should NOT illuminate. Is the test lamp OFF? | -- | Go to Step 8 | Go to Step 11 | ||||||||||||
8 |
Is the amperage within the specified range? | 100-200 mA | Go to Step 14 | Go to Step 9 | ||||||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 | ||||||||||||
10 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
11 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
12 | Repair the switched B+ circuit to the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||||
13 | Replace the fuel pump relay. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||||
14 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||||||
|
Important:
Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the action? | -- | Go to Step 16 | -- | |||||||||||||
16 |
Does the DTC run and pass? | -- | Go to Step 17 | Go to Step 2 | ||||||||||||
17 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||||||
