For 1990-2009 cars

Refer to

#### Injector Circuits

Engine Controls Components
Powertrain Control Module Description
Information Sensors
Fuel System
OBD II Symbol Description Notice
Ignition Switch and Underhood Electrical Center 2
U/H Center 2: INJ 1 and INJ 2 Fuses
U/H Center 2: INJ 1 and INJ 2 Fuses
Powertrain Control Module Connector End Views
for complete circuit details.

### Circuit Description

The PCM enables an injector on the intake stroke of each cylinder. Individual cylinder fuel control is referred to as Sequential Multi-port Fuel Injection (SFI).

Ignition voltage is supplied directly to the fuel injectors. The PCM controls each injector by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver or control circuit is equipped with a fault line which is monitored by the PCM. When the PCM is commanding an injector ON, the voltage of the control circuit should be low. When the PCM is commanding the injector OFF, the voltage potential of the control circuit should be high. If the PCM detects the injector control circuit voltage other than what is expected, the PCM sets a DTC.

### Conditions for Running the DTC

• | The engine speed is greater than 400 RPM.

• | The ignition voltage is greater than 6.0 volts but less than 18.0 volts.

### Conditions for Setting the DTC

The PCM detects the wrong voltage potential on any injector driver circuit for 5.0 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Use a scan tool in order to clear the MIL and the DTC.

### Diagnostic Aids

Important:

• | Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.

• | For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems for procedures.

• | The following may cause an intermittent:

- | Poor connections: Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

- | Corrosion

- | Mis-routed harness

- | Rubbed through wire insulation

- | Broken wire inside the insulation

• | A misfire may not be apparent at idle. The misfire may only occur above idle under a load. Road test the vehicle and monitor the misfire current counters.

• | Observe, if more then one cylinder is mis-firing, the scan tool may only display one cylinder mis-firing. This will not be apparent until the repair is completed. Also, if an injector fuse is open for one side of the engine, the scan tool may only display 2 or 3 cylinders mis-firing.

• | When the injector driver is disabled, an engine misfire will be apparent and a misfire DTC sets.

• | Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed

• | For an intermittent condition, refer to Symptoms .

### Test Description

The numbers below refer to step numbers on the diagnostic table.

1. This step determines if a malfunction is present.

   The Misfire current counters will not increment if certain DTCs set at the same time or after DTC P0300 sets. Refer to conditions for running DTC P0300 for applicable DTC list.

   If more than one cylinder is misfiring, the Misfire current counters may increment for only one cylinder. Example: Cylinders 1 and 8 are both misfiring, yet only cylinder 8 increments on the Misfire current counter.

   If one injector fuse open, only two or three Misfire current counters may increment for the corresponding side of the engine.

2. There are two ways to isolate a malfunctioning injector circuit:

• | DTC P0300 indicates a misfire is present. So use the misfire current counters to locate the cylinder that is misfiring.

• | If no misfire DTC is present, Start and idle the engine while monitoring misfire current counters. If a misfire is present, the misfire current counters will increase for a cylinder that has a misfire.

3. The injector fuses also feed the ignition coil/modules. Thoroughly inspect the circuits going to the ignition coil/modules for a short to ground. A shorted ignition coil/module may also cause a fuse to open.

4. Inspect the injector connections before replacing the injector. A faulty connection causes an inoperative injector.

5. Disconnecting the PCM allows using the DMM to test continuity of the circuits. This aids in locating an open or shorted circuit. Tests for an ignition feed circuit that is shorted to ground.

6. Tests for an ignition feed circuit that is shorted to ground.

#### Fuel Injector Circuit Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Install the scan tool.
2. Start the engine.
3. Monitor all the Misfire Current Counters on the Misfire Data List (There are a total of 8 counters. One counter per cylinder) using a scan tool.

Are any of the Misfire Current Counters incrementing?

--

Go to Step 4

Go to Step 3

3 | Monitor the Misfire History Counters on the Misfire Data List (There are a total of 8 counters. One counter per cylinder) using a scan tool. Do any of the Misfire History Counters indicate a number other than 0.0 counts? | -- | Go to Step 18 | Go to Diagnostic Aids
4 | Are the injector fuses OK? | -- | Go to Step 5 | Go to Step 8
5 |

1. Turn OFF the ignition.
2. Disconnect the injector(s) harness that the Misfire Current counter is incrementing for.
3. Turn ON the ignition leaving the engine OFF.
4. Probe the injector harness ignition feed circuit using the test lamp J 35616-200 connected to ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 10

6 |

1. Turn OFF the ignition.
2. Connect the injector test lamp J 34730-2C to the isolated injector harness.
3. Start the engine.

Does the test lamp blink?

--

Go to Step 7

Go to Step 11

7 |

1. Inspect the injector harness terminals for poor connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 9

8 |

1. Turn OFF the ignition.
2. Disconnect the four injector harness connectors related to the fuse that was open.
3. Probe the injector ignition feed circuits of one of the injector harnesses that are disconnected using the test lamp J 35616-200 connected to B+.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 9

9 | Important: Return to this Diagnostic after performing the Fuel Injector Coil Test. Perform the Fuel Injector Coil Test. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) . Did any of the Fuel Injectors require replacement? | -- | Go to Step 19 | Go to Step 14
10 | Repair the injector ignition feed circuit to the isolated injector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 19 | --
11 |

1. Turn OFF the ignition.
2. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
3. Test the injector driver circuit for an open or short to ground.

Is the injector driver circuit open or shorted to ground?

--

Go to Step 12

Go to Step 16

12 | Repair the injector driver circuit for an open, short to ground, or a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 19 | --
13 |

1. Repair the grounded ignition feed circuit to the injectors. Refer to Wiring Repairs in Wiring Systems.
2. Replace the open fuse.

Is the action complete?

--

Go to Step 19

--

14 | Repair intermittent short to ground in the injector ignition feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 19 | --
15 | Replace the faulty injector(s) that was isolated. Refer to Fuel Injector Replacement . Is the action complete? | -- | Go to Step 19 | --
16 |

1. Inspect for poor connections at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 17

17 | Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 19 | --
18 |

1. Inspect the appropriate injector circuit for the following:

• | Poor connections at the injector and the PCM terminal.

• | Intermittent shorts to ground.

• | Intermittent opens. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

2. If a condition is found, repair as necessary.

Did you find and correct the condition?

--

Go to Step 19

Go to Symptoms

19 |

1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 20

Go to Step 2

20 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK