Schematic Reference: Engine Controls Schematics
Circuit Description
The sequential multiport fuel injection (SFI) system is controlled by the powertrain control module (PCM). The PCM energizes the solenoid coil of each fuel injector individually by completing the electrical circuit to ground. When energized the fuel injector solenoid operates the solenoid plunger, allowing pressurized fuel to be injected into the intake port of the cylinder. The fuel pump will pressurize the fuel rail and the fuel injectors as long as the engine is cranking, and the PCM is receiving ignition system reference pulses.
Diagnostic Aids
Check for any of the following conditions:
| • | Water, contaminated fuel, or inferior quality fuel can cause a no start or hard start condition even though the fuel injectors and circuitry are OK. |
| • | Check for a faulty spray pattern from the fuel injector nozzle if both the fuel injector solenoid and the fuel injector circuit are OK. |
| • | There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and their circuit are OK, and fuel spray is detected, some fuel injector nozzles may be partly blocked or restricted. If the PCM receives incorrect inputs from the various information sensors the fuel delivered by the fuel injectors may be inadequate to start the engine. Check all engine data parameters with a scan tool and compare the values indicated with expected values or values on a known good vehicle. |
| • | Normal fuel injector resistance is 13.4-14.4 ohms at 20°C (68°F). |
| • | If you were sent here by a DTC P0300 and all the injectors checked OK, the Misfire Current Cylinder information on a scan tool can be used to determine which injector circuit should be examined more closely. |
| Check the engine electrical ground G106 (four wires) at the rear of the cylinder head, if there is spark but no fuel injector pulse. |
An intermittent malfunction may be caused by a fault in the fuel injector electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | Broken conductor inside the wire insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
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 for fuel injector control signals from the PCM.
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This step checks for a fault that affects all the fuel injectors.
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This step checks for a short in the fuel injector control circuit.
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This step checks for ignition positive voltage.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic System Check? | -- | |||||||
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Important: This table assumes that the MIL and the DLC function normally. Check that MIL operation and DLC communication is OK before using this table.
Did the injector test lamp flash for each injector circuit while cranking the engine? | -- | |||||||
3 | Did the fuel injector test lamp flash for at least one fuel injector circuit while cranking the engine? | -- | ||||||
4 |
Is the action complete? | -- | -- | |||||
Was the injector test lamp illuminated steady for any fuel injector circuit? | -- | |||||||
6 |
Is the fuel injector test lamp illuminated | -- | ||||||
7 | Repair the short to ground in the faulty fuel injector control circuit between the PCM and the fuel injector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
Did the test lamp illuminate? | -- | |||||||
9 | Repair the open in the ignition feed circuit between the fuel injector and splice S204. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
10 |
Was a repair necessary? | -- | ||||||
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||
12 | Perform the scan tool Clear DTC Information function and road test the vehicle within the conditions that caused the concern. Does the system now operate properly? | -- | System OK | Go to Diagnostic Aids |
