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Makes 🢒 GMC_Truck 🢒 2001 🢒 Savana 🢒 Bulletins 🢒 SMU - Revised Diagnostic System Check-Engine Controls

SMU - Revised Diagnostic System Check-Engine Controls

Subject:Revised Diagnostic System Check-Engine Controls

Models:2001-2002 Chevrolet Express Van
2001-2002 GMC Savana Van
with 6.5L Engine (VIN F - RPO L65)


This bulletin is being issued to revise the Diagnostic System Check-Engine Controls in the Engine Controls sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

Test Description

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

  1. Lack of communication may be because of a partial or a total malfunction of the class 2 serial data circuit. The specified procedure determines the particular condition.

    2.

  2. This step stores the powertrain control module (PCM) diagnostic trouble code (DTC) information into the scan tool's memory. After you complete the diagnostic procedure, review the captured information in order to catch the next DTC if the control module stores multiple DTCs. Review the Freeze Frame data and the Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information may help diagnose an intermittent condition. Information about the operating conditions at the time that the DTC set may also help diagnose an intermittent condition. Capturing the stored information saves the data that the PCM loses during the following conditions:

    3. • When a diagnostic procedures instructs you to clear the DTCs.
    • When a diagnostic procedure instructs you to disconnect the PCM connectors.
    • When a diagnostic procedure instructs you to replace the PCM.

  3. The presence of DTCs which begin with "U", indicate that some other module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.

    4.

  4. If there are other modules with DTCs set, refer to the DTC list. The DTC list directs you to the appropriate diagnostic procedure.

    If the control module stores multiple powertrain DTCs, diagnose the DTCs in the following order:

    5. • Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs. Diagnose the multiple DTCs within this category in numerical order. Begin with the lowest numbered DTC, unless the diagnostic table directs you otherwise.
    • System level DTCs, for example, misfire DTCs, fuel trim DTCs, and catalyst DTCs.

  5. This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more I/M system statuses that did not set.

A Diagnostic System Check for Engine Controls

Step

Action

Yes

No

Important: 

   • DO NOT perform this diagnostic if there is not a driveability concern, unless another procedure directs you to this diagnostic.
   • Before you proceed with diagnosis, search for applicable service bulletins.
   • Unless a diagnostic procedure instructs you, DO NOT clear the DTCs.
   • If there is a condition with the starting system, refer to Diagnostic System Check - Engine Electrical in Engine Electrical.
   • Ensure the battery has a full charge.
   • Ensure the battery cables are clean and tight.
   • Ensure the PCM grounds are clean, tight, and in the correct location.

1

Connect a scan tool.

Does the scan tool turn ON?

Go to Step 2

Go to Scan Tool Does Not Power Up in Data Link Communications

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information using the Class 2 Message Monitor feature:
    3. • The powertrain control module (PCM)
    • The electronic brake control module (EBCM)
    • The passlock module
    • The vehicle immobilizer module

Does the scan tool communicate with all the listed control modules?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Attempt to start the engine.

Does the engine start and idle?

Go to Step 4

Go to Engine Cranks but Does Not Run

4

Select the DTC display function for the following control modules:

    • The PCM
    • The EBCM

Does the scan tool display any DTCs?

Go to Step 5

Go to Step 10

5

With a scan tool, select Captured Info in order to store the powertrain DTC information.

Did you complete the action?

Go to Step 6

--

6

Does the scan tool display DTCs which begin with a "U"?

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

Go to Step 7

7

Does the scan tool display DTC P0251 and P0606?

Go to DTC P0251

Go to Step 8

8

Does the scan tool display DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627 or P1683?

Go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

Go to Step 9

9

Does the scan tool display DTC P0562, P0563, P1637, or P1638?

Go to Diagnostic System Check - Engine Electrical in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List

10

Is the customer's concern with the automatic transmission?

Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission in Automatic Transmission 4L80-E

Go to Step 11

11

Is the customer's concern with Inspection and Maintenance (I/M) testing?

Go to Inspection/Maintenance (I/M) System Check

Go to Step 12

12
  1. Review the following symptoms.
  2. Refer to the applicable symptom diagnostic table:
    3. • Hard Start
    • Surges/Chuggles
    • Lack of Power, Sluggishness, or Sponginess
    • Fuel Knock/Combustion Noise
    • Hesitation, Sag, Stumble
    • Cuts Out, Misses
    • Poor Fuel Economy
    • Excessive Smoke

Did you find and correct the condition?

System OK

Go to Intermittent Conditions