GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Express (CNG) 🢒 DTC 🢒 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 PCM by dedicated pulse width modulated (PWM) circuits.

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

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. If any of the listed DTCs are set, diagnose those DTCs first.

    3.

  3. This step tests the signal circuit of the FRT sensor. The DMM should display 5 volts.

    4.

  4. This step tests the low reference circuit of the FRT sensor. An open FRT sensor low reference circuit may cause this DTC to set.

    5.

  5. This step determines if the FICM, PCM, and the rail temperature output PWM circuit are OK. If the temperature parameter changes when the FRT signal circuit is grounded, the FICM, PCM, and wiring are OK. Repeat the procedure as necessary in order to verify correct operation of the FICM, PCM, and the rail temperature output PWM circuit.

    6.

  6. This step verifies that the FICM is supplying the correct output voltage. The open circuit voltage should be 5.0 volts.

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 4

3

Are any of the DTCs P0187, P0188, P0191, P0192, P0193, or P0611 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 5

4
  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 5

Go to Intermittent Conditions

5

  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the FRT sensor. Refer to Fuel Temperature Sensor Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the signal circuit of the FRP sensor with a DMM.

Does the DMM display a voltage near the specified value?

5.0 V

Go to Step 7

Go to Step 6

6

Is the voltage above the specified value?

5.3 V

Go to Step 14

Go to Step 13

7

Probe the low reference circuit of the FRT sensor with a test lamp connected to B+.

Is the test lamp illuminated?

--

Go to Step 8

Go to Step 15

8

  1. Observe the FRT sensor temperature parameter with a scan tool.
  2. Jumper the signal circuit of the FRT sensor to a known good ground.

Does the FRT temperature display fluctuate when the circuit is grounded?

--

Go to Step 16

Go to Step 9

9

  1. Turn OFF the ignition.
  2. Connect the harness connector of the FRT sensor.
  3. Disconnect the PCM harness connector C2. Refer to Powertrain Control Module Replacement in Engine Controls in the G/H Van Service Manual.
  4. Turn ON the ignition, with the engine OFF.
  5. Measure the voltage from the rail temperature output PWM circuit with a DMM.

Does the DMM display the voltage at the specified value?

5.0 V

Go to Step 17

Go to Step 10

10

Is the voltage more than the specified value?

5.3 V

Go to Step 12

Go to Step 11

11

Test for an open, or a short to ground 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 22

Go to Step 18

12

Test for a short to voltage 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 22

Go to Step 21

13

Test for an open on the signal circuit of the FRT sensor. 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 22

Go to Step 18

14

Test for a short to voltage on the signal circuit of the FRT sensor. 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 22

Go to Step 21

15

Test for an open on the low reference circuit of the FRT sensor. 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 22

Go to Step 18

16

Inspect for proper terminal contact at the harness connector of the FRT sensor. 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 22

Go to Step 19

17

Inspect for proper terminal contact at the harness connector of the 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 22

Go to Step 20

18

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 22

Go to Step 21

19

Replace the FRT sensor. Refer to Fuel Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 22

--

20

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 22

--

21

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

Did you complete the replacement?

--

Go to Step 22

--

22
  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 23

23

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