GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.8L (L26 and L32) 🢒 DTC P1374

Circuit Description

The powertrain control module (PCM) uses the 3X reference pulses from the ignition control module (ICM) to calculate engine RPM, and crankshaft position at engine speeds above 1,200 RPM. The 3X reference signal is produced by the ICM and passed to the PCM on the low-resolution engine speed signal circuit. The PCM constantly compares the number of 18X reference pulses to the number of 3X reference pulses and camshaft position signals being received. If this DTC sets, the engine will continue to start and run using the cam signal and 18X reference pulses. The PCM will use the medium-resolution engine speed signal circuit for fuel injection and ignition control. If the PCM detects an incorrect number of 3X pulses during two crankshaft revolutions, DTC P1374 sets.

Conditions for Running the DTC

The engine is running for more than 3 seconds.

Conditions for Setting the DTC
    • The PCM detects an incorrect number of 3X reference pulses during two crankshaft revolutions.
    • The above conditions are present for up to 30 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the 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.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module 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
  1. Start the engine.
  2. Observe the 3X crank sensor parameter with a scan tool.

Does the 3X crank sensor parameter vary with engine RPM?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition.
  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/Failure Records.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the ignition control module (ICM).
  3. Turn ON the ignition, with the engine OFF.
  4. Momentarily probe the low resolution engine speed signal circuit at the ICM harness connector with a test lamp connected to B+.
  5. Observe the engine speed parameter on the scan tool.

Is an engine speed displayed?

Go to Step 8

Go to Step 5

5

Test for the following conditions in the low resolution engine speed signal circuit between the ICM and the powertrain control module (PCM):

    • An open
    • A short to voltage
    • A short to ground

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 6

6

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

Inspect for the following conditions:

    • Harnesses routed near secondary ignition components
    • Arcing from the ignition coil to the wiring harness or to the ignition control module

       Important: If carbon tracking is detected on any component, replace that component and its mate.

    • Cracks, carbon tracking, or other signs of damage at the ignition coil--Refer to Ignition Coil Replacement .
    • Arcing from the secondary ignition wires to the wiring harness--Refer to Spark Plug Wire Replacement .

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Test for an intermittent and for a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems .

Did you find and correct the condition?

Go to Step 11

Go to Step 9

9

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

Go to Step 11

--

10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 11

--

11
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition.
  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/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 12

12

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