For 1990-2009 cars

### Circuit Description

The control module enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

### Diagnostic Aids

• | Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.

• | Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.

• | Perform the fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Observe the ECT Sensor parameter with a scan tool. Is the ECT Sensor parameter within the specified range? | 10-32°C (50-90°F) | Go to Step 3 | Go to Step 4
3 |

1. Remove the air cleaner outlet resonator.
2. Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems.

Is the resistance within the specified range for each injector?

11-14 ohms

Go to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2

Go to Step 6

4 |

1. Remove the air cleaner outlet resonator.
2. Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems.
3. Record each fuel injector resistance value.
4. Subtract the lowest resistance value from the highest resistance value.

Is the difference equal to, or less than, the specified value?

3 ohms

Go to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2

Go to Step 5

5 |

1. Add all of the fuel injector resistance values to obtain a total resistance value.
2. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value.
3. Subtract the lowest individual fuel injector resistance value from the average resistance value.
4. Compute the difference between the highest individual fuel injector resistance value and the average resistance value.
5. Replace the fuel injector that displays the greatest resistance difference above or below the average. Refer to Fuel Injector Replacement .

Did you complete the replacement?

--

Go to Step 7

--

6 | Replace the fuel injector or fuel injectors with resistance that is out of the specified range. Refer to Fuel Injector Replacement . Did you complete the replacement? | 11-14 ohms | Go to Step 7 | --
7 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2