GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Express (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 DTC P1208

Circuit Description

The fuel injector control module (FICM) monitors the fuel rail pressure (FRP) sensor voltage, and the fuel rail temperature (FRT) sensor voltage. The FICM communicates the data to the powertrain control module (PCM) by dedicated pulse width modulated (PWM) circuits.

This DTC sets when the rail temperature output PWM signal is not received by the PCM.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1208 Fuel Injector Control Module Sensor Signal Circuit 2

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC
    • The fuel rail temperature output PWM signal is not received by the PCM.
    • The condition exists for at least 5 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module switches over to gasoline fuel operation.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

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

  1. This step determines if the condition is present.

    2.

  2. The sensor DTCs should be diagnosed prior to this DTC.

    3.

  3. DTC P0611 should be diagnosed prior to this DTC when 2 or more of the listed DTCs are also set.

    4.

  4. This step tests for the proper voltage from the PCM.

    5.

  5. By intermittently probing the PWM circuit, you are simulating a PWM signal. The sensor voltage display will remain at 0 volts, however the temperature display should fluctuate.

    6.

  6. A voltage higher than 5.3 volts indicates a short to battery.

    7.

  7. This step tests the PWM circuit for a short to ground.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

Observe the FICM even bank circuit status with a scan tool.

Does the scan tool display FAULT?

--

Go to Step 3

Go to Step 5

3

Do any of the DTCs P0187, P0188, P0191, P0192 or P0193 also set this ignition?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 4

4

Observe the DTC information for the following DTCs:

    • P1207
    • P1208
    • P1209

Are 2 or more of the listed DTC's set or is this DTC set with an engine cranks but does not start condition?

--

Go to DTC P0611

Go to Step 6

5
  1. Observe the Freeze Frame and/or the Failure records data for this DTC.
  2. Turn the ignition OFF for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data.

Does the DTC fail this ignition cycle?

--

Go to Step 2

Go to Intermittent Conditions

6

  1. Turn OFF the ignition.

    2. Important: Other DTCs may set.

  2. Disconnect the fuel injector control module (FICM) harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the rail temperature output pulse width modulated (PWM) circuit with a DMM.

Does the DMM display the voltage at the specified value?

5.0 V

Go to Step 7

Go to Step 8

7

  1. Observe the fuel rail temperature (FRT) sensor temperature parameter with a scan tool.
  2. Repeatedly and rapidly probe the rail temperature output PWM circuit with a test lamp connected to ground.

Does the FRT temperature display fluctuate when the circuit is repeatedly probed with the test lamp?

--

Go to Step 13

Go to Step 16

8

Is the voltage more than the specified value?

5.3 V

Go to Step 12

Go to Step 9

9

  1. Turn OFF the ignition.
  2. Probe the rail temperature output PWM circuit with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 10

10

Test for an open on the rail temperature output PWM circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 14

11

Repair the short to ground on the rail temperature output PWM circuit. Refer to Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you correct the condition?

--

Go to Step 17

--

12

Repair the short to voltage on the rail temperature output PWM circuit. Refer to Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you correct the condition?

--

Go to Step 17

--

13

Inspect for proper terminal contact at the harness connector of the FICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 15

14

Inspect for proper terminal contact at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 16

15

Replace the FICM. Refer to Fuel Injector Control Module Replacement .

Did you complete the replacement?

--

Go to Step 17

--

16

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the G/H Van Service Manual.

Did you complete the replacement?

--

Go to Step 17

--

17
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 18

18

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK