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 DTC will set.
When the ECM detects any reference pulses from the crankshaft position 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 powerdown 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 ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
Notice: Using the J 35616-A Connector Test Adapter Kit will prevent damage to the harness connector terminals.
Use theJ 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 Engine Control Module Diagnosis for the proper procedure. |
| • | Inspect all circuits that are spliced to the fuel pump relay B+ circuits for the proper operation. |
| • | 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 Wiring Repairs 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 | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | Go to Step 2 | |||||||||||||
Does the relay turn ON and OFF with each command? | -- | Go to Step 3 | Go to Step 5 | |||||||||||||
Does the current draw measure within the range shown? | 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 a J 35616-200 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 a J 35616-200 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 |
Does the current draw measure within the range shown? | 100-200 mA | Go to Step 14 | Go to Step 9 | ||||||||||||
9 |
Was a wiring repair necessary? | -- | Go to Step 16 | Go to Step 13 | ||||||||||||
10 |
Was a wiring repair necessary? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
11 |
Was a wiring repair necessary? | -- | 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. Is the action complete? | -- | Go to Step 16 | -- | ||||||||||||
13 | Replace the fuel pump relay. Is the action complete? | -- | Go to Step 16 | -- | ||||||||||||
14 |
Did you find and correct a problem? | -- | Go to Step 16 | Go to Step 15 | ||||||||||||
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Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 16 | -- | |||||||||||||
16 |
Does the scan tool indicate that the diagnostic Passed? | -- | Go to Step 17 | Go to Step 2 | ||||||||||||
17 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
