GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD (LPG) 🢒 DTC 🢒 DTC P0336

Circuit Description

The powertrain control module (PCM) monitors the crankshaft position sensor (CKP) signal in order to determine engine speed. The PCM signals engine speed to the Alternative Fuels ECM by pulse-width-modulating the engine speed signal circuit.

This DTC indicates no engine speed signal is being monitored by the Alternative Fuels ECM while the MAF sensor signal indicates the crankshaft is rotating.

Conditions for Running the DTC
    • No Alternative Fuels ECM MAF sensor DTCs are set this ignition cycle.
    • The MAP sensor signal indicates 105.23 kPa (31.07 in Hg) or less.
    • The mass air flow is more than 3 grams per second for 1 second continuously.

Conditions for Setting the DTC

The Alternative Fuels ECM does not monitor an engine speed signal during the 1 second that mass air flow is more than 3 grams per second.

Action Taken When the DTC Sets
    • The Alternative Fuels ECM will switchover to gasoline operation on KL6 equipped vehicles.
    • The Alternative Fuels ECM will illuminate the MIL and store the DTC as History during 1 drive trip in which the diagnostic runs and fails.
    • The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • The Last Test Failed status will clear when the DTC runs and passes.
    • The Alternative Fuels ECM will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
    • The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared 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 causing a no start.

    2.

  2. This step determines if the condition affects the PCM.

    3.

  3. This step determines if the fault is present.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

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

Crank and attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 3

Go to Step 5

3

With a scan tool, establish communication with the PCM, and review DTC information.

Is DTC P0335 stored in the PCM?

--

Go to DTC P0335 in Engine Controls in the C/K Pickup Service Manual

Go to Step  4

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.
  5. Monitor the Alternative Fuels ECM DTC information with a scan tool.

Does the DTC fail this ignition cycle?

--

Go to Step 12

Go to Intermittent Conditions

5
  1. With a scan tool establish communications with the PCM.
  2. Observe the RPM data display.
  3. Crank the engine.

Does the scan tool display RPM as the engine is cranking?

--

Go to Step 12

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Disconnect the CKP sensor. Refer to Crankshaft Position Sensor Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Measure voltage from the ignition feed circuit of the CKP sensor with a DMM.

Does the DMM display the specified value?

B+

Go to Step 7

Go to Step 13

7

Measure the voltage between the ignition feed circuit and the low reference circuit of the CKP sensor with a DMM.

Does the DMM display the specified value?

B+

Go to Step 8

Go to Step 14

8
  1. Observe the RPM data display, in the PCM data list, with a scan tool.
  2. Momentarily probe the sensor circuit of the CKP sensor with a test lamp connected to B+.

Does the RPM data display increment when the test lamp contacts the sensor circuit?

--

Go to Step 15

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement in Engine Controls in the C/K Pickup Service Manual.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the CKP sensor signal circuit with a DMM.

Does the DMM display near the specified value?

1.5 Volts

Go to Step 20

Go to Step 10

10

Test the CKP sensor signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 11

11

Test the CKP sensor signal circuit for an open or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

12

Test the CKP sensor signal circuit for an open between the Alternative Fuels ECM and the splice. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

13

Test the ignition feed circuit of the CKP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 17

14

Test the low reference circuit of the CKP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 17

15

Inspect for proper terminal contact at the harness connector of the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

16

Inspect for proper terminal contact at the harness connector of the Alternative Fuels ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

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 C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

18

Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 21

--

19

Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 21

--

20

Important: KL6 models require a switchover to gasoline with a scan tool in order to perform the Crankshaft Position Variation Learn Procedure.

KL8 models do not require the Crankshaft Position Variation Learn Procedure.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 21

--

21
  1. Use the scan tool in order to clear the DTCs from the following control modules:
    2. • Alternative Fuels ECM
    • PCM
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 22

Go to Step 2

22

With a scan tool, select Capture Info in order to observe the stored information.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK