Schematic Reference: Engine Controls Schematics
Circuit Description
The Engine Control Module (ECM) will energize the fuel pump relay for 3 seconds when the ignition switch is turned to the ON position. When the fuel pump relay is energized the fuel pump will operate and pressurize the fuel system. When the engine is being cranked, or is running, the ECM will receive ignition system reference pulses and will continue to energize the fuel pump relay as long as the ignition system reference pulses are detected. The fuel pump will stop after 3 seconds when the ignition is ON, unless the ECM receives ignition system reference pulses.
Diagnostic Aids
A restricted or leaking fuel feed pipe or hose will cause an Engine Cranks But Will Not Start condition. Check the fuel sender assembly connections inside of the fuel tank for poor connections.
An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks the fuel pump operation with the ignition switch in the ON position.
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This step checks for an open in the fuel pump relay control circuit before the replacement of the ECM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Did the fuel pump operate for approximately 3 seconds? | -- | ||
3 |
Is the test light ON while the engine is cranking? | -- | Go to Fuel System Diagnosis | |
4 |
Is the test light ON? | -- | ||
5 |
Is the fuel pump ON? | -- | ||
6 |
Is test light ON? | -- | ||
7 |
Is the test light ON? | -- | ||
8 | Replace the fuel pump. Refer to Fuel Pump Replacement. Is the action complete? | -- | -- | |
9 | Repair the open or short in the BLU/BLK wire between the main relay and the fuel pump relay. Is the action complete? | -- | -- | |
10 | Repair the open or short in the PNK/BLK wire between the fuel pump and the fuel pump relay. Is the action complete? | -- | -- | |
11 | Repair the faulty ground connection or the open in the fuel pump ground circuit. Is the action complete? | -- | -- | |
12 |
Is the test light ON? | -- | ||
13 | Probe the fuel pump relay connector cavity 3 with the test light connected to B+. Does the test light illuminate while cranking the engine? | -- | ||
14 | Backprobe the fuel pump relay control circuit at the ECM with the test light connected to B+. Does the test light illuminate while cranking the engine? | -- | ||
15 | Repair the open or the short in the BLK/WHT wire. Is the action complete? | -- | -- | |
16 | Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement. Is the action complete? | -- | -- | |
17 | Check for an open in the fuel pump relay circuit between the fuel pump relay and the ECM. Repair as necessary. Was a repair necessary? | -- | ||
18 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
19 | Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK | Go to Diagnostic Aids |
