GM Service Manual Online
For 1990-2009 cars only

Description

Important: Do not perform this check if no driveability concern exists.

The Powertrain OBD System Check is an organized approach to identifying a problem created by an electronic powertrain control system malfunction. The Powertrain OBD System Check is the starting point for any driveability concern diagnosis. The Powertrain OBD System Check directs the service technician to the next logical step in diagnosing a driveability concern. Understanding and using the table correctly will reduce the diagnostic time and prevent the replacement of good parts.

Important: For automatic transmission DTCs, refer to Diagnostic Trouble Code Identification in Transmission (4L60E) or Diagnostic Trouble Code Identification in Transmission 4L80E) for diagnosis procedures. The DTCs associated with the automatic transmission are:

   • DTCs P0502 and P0503.
   • Any 700 (except P0704, P0705 and P0706) and 1800 series DTCs (i.e. DTC P07XX and P18XX).

Important: For Domestic and Export DTC Types, refer to Diagnostic Trouble Code (DTC) List .

Important: When the Body Control Module (BCM) is replaced the PCM Password Learn procedure must be performed. Refer to DTC P1631 Theft Deterrent Start Enable Signal Not Correct . DTC P1631 sets if the password learn procedure is not performed.

Important: This vehicle is equipped with a Powertrain Control Module (PCM) utilizing an Electrically Erasable Programmable Read Only Memory (EEPROM). Program the new PCM when diagnostics call for replacement of the PCM. When the PCM is replaced the following must be performed:

  1. The PCM must be programed. Refer to Powertrain Control Module Replacement/Programming .
  2. The PCM Password Learn procedure. Refer to DTC P1631 Theft Deterrent Start Enable Signal Not Correct for details on procedure.
  3. The CKP System Variation Learn procedure. Refer to Crankshaft Position System Variation Learn .
  4. The Idle Learn procedure. Refer to PCM Idle Learn Procedure .
  5. When the PCMs power is interrupted or is reprogrammed, the Idle Learn procedure must be performed. Refer to PCM Idle Learn Procedure .

Diagnostic Aids

Important: If an intermittent condition exists, inspect the PCM wiring harnesses for improper installation of electrical components. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. Ensure that no aftermarket equipment is connected to the Class 2 circuit. A cellular phone signal communication may cause an intermittent condition.

Test Description

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

  1. Use a properly functioning scan tool with the diagnostic tables in this section. DO NOT use the Clear Info function unless instructed by a diagnostic procedure.

  2. This step checks that the scan tool communicates with the PCM.

  3. This step checks that the scan tool communicates with all other modules on the Class 2 Circuit.

  4. An ignition 1 voltage that is too low may cause the following conditions:

  5. • A no start
    • Stalling
    • High idle
    • An inoperative scan tool
  6. This step checks for DTCs associated with the Vehicle Theft Deterrent (VTD) system which will prevent the engine from starting. A problem with the BCM causes this condition. If the BCM is not powered up, the PCM does not receive a password and the engine starts and stalls.

  7. If the VCM/PCM Fuel Continue parameter displays NO, this indicates the BCM is not sending the PCM the password.

  8. If multiple DTCs are stored, diagnose in the following order of priority:

  9. 1. PCM failure DTCs (P0601, P0602, P0604)
    2. System Voltage DTCs
    3. Component level DTCs (Sensors, Solenoids, Relays etc.). Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC.
    4. System level DTCs (Misfire, Fuel Trim, etc.)

For Automatic Transmission DTCs, Refer to Diagnostic Trouble Code Identification (4L60-E) or Diagnostic Trouble Code Identification (4L80-E) in Automatic Transmission.

It is beneficial to review the Freeze Frame Data and/or Fail Records. Use the odometer information and the fail counter in order to determine how frequently and how recently the DTC set. This information and the other operating conditions when the DTC set may help diagnose an intermittent problem. Capturing the stored info preserves data that the PCM will lose when instructed to Clear Info at the end of a diagnostic table, or if you disconnect the PCM or replace the PCM during a diagnostic procedure. The scan tool stores the data in the scan tool's memory. Review the captured info at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored. Follow the order of priority as listed above.

  1. Compare actual control system data with the values in the Engine Scan Tool Data List to determine if any parameter is not within limits. Keep in mind that a base engine problem (i.e. advanced cam timing) may substantially alter sensor values. If the actual data does not correspond with the values in the Engine Scan Tool Data List , refer to the appropriate system/component diagnostic aids or test descriptions.

Step

Action

Value(s)

Yes

No

1

Important: 

   • Check for applicable service bulletins before proceeding with diagnosis.
   • Do not turn the ignition OFF when performing this Diagnostic table.
   • Ensure the battery is fully charged before proceeding with this diagnostic.
   • Save or Capture the DTC Freeze Frame and/or Failure Records information using a scan tool.

  1. Connect a scan tool to the Data Link Connector (DLC).
  2. Turn ON the ignition leaving the engine OFF.

Does the scan tool power-up?

--

Go to Step 2

Go to Data Link Connector Diagnosis

2

Does the scan tool display PCM data?

--

Go to Step 4

Go to Step 3

3

Use a scan tool in order to select the Diagnostic Circuit check and the Class 2 Message Monitor.

Does the scan tool display any other modules as active?

--

Go to Data Link Connector Diagnosis

Go to Data Link Communications System Check in Wiring Systems

4

Important: If the starter does not engage, refer to Starting System Check in Engine Electrical.

Monitor the Ignition 1 voltage using a scan tool while cranking the engine or while the engine is operating.

Is the Ignition 1 voltage near the specified voltage?

B+

Go to Step 5

Go to DTC P0562 System Voltage Low

5

Does the engine start and continue to operate?

--

Go to Step 8

Go to Step 6

6

Are there any PCM/BCM DTCs related to vehicle theft deterrent system set?

--

Go to applicable DTC

Go to Step 7

7

Monitor the VCM/PCM Fuel Continue parameter using a scan tool in Body while cranking the engine.

Does the scan tool display VCM/PCM Fuel Continue as NO?

--

Go to Vehicle Theft Deterrent (VTD) System Check in Theft Deterrent

Go to Engine Cranks but Does Not Run

8

Important: Save or capture the DTC Freeze Frame and/or Failure Records information using a scan tool.

Monitor the DTC information using a scan tool.

Are any DTCs displayed?

--

Go to the applicable DTC table

Go to Step 9

9

Compare the scan tool data with the values shown in the Engine Scan Tool Data List .

Are the values normal or within typical ranges?

--

Go to Symptoms

Go to Diagnostic Aids and Test Descriptions