SMU - Revised Diagnostic System Check-Engine Controls. GMC Truck GMC K Sierra

Subject:

Revised Diagnostic System Check-Engine Controls

Models:

2001 Chevrolet Silverado, Suburban, Tahoe

2001 GMC Sierra, Yukon, Yukon Denali, Yukon XL

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, U -- RPOs LR4, LM7, LQ4)

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.

Description

The Diagnostic System Check-Engine Controls is an organized approach to identifying a condition that is created by a malfunction in the engine control system. The Diagnostic System Check must be the starting point for any driveability concern. The Diagnostic System Check directs the service technician to the next logical step in order to diagnose the concern. Understanding and correctly using the diagnostic table reduces diagnostic time and prevents the replacement of good parts.

Test Description

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

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.

This step stores the PCM 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:

•	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.

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.

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:

•	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.

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.

Step

Action

Yes

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.

Install 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

Turn ON the ignition, with the engine OFF.
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.

•

PCM

•

VTD

•	IP Cluster

•

EBCM

•

HVAC

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

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank Power mode.

Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
Rotate the ignition switch through all positions while observing the ignition switch Power Mode parameter. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems for a list of the power mode states that correspond to each ignition switch position.

Does the ignition switch parameter reading match the ignition switch position for all switch positions?

Go to Step 4

Go to Power Mode Mismatch in Body Control Systems

Attempt to start the engine.

Does the engine start and idle?

Go to Step 5

Go to Engine Cranks but Does Not Run

Select the DTC display function for the following control modules:

•

PCM

•

VTD

•	IP Cluster

•

EBCM

•

HVAC

Does the scan tool display any DTCs?

Go to Step 6

Go to Step 10

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

Did you complete the action?

Go to Step 7

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 8

Does the scan tool display DTC P0601, P0602, P0604 or P0606?

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

Go to Step 9

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

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List

Is the customer's concern with the automatic transmission?

Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission

Go to Step 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

Review the following symptoms.
Refer to the applicable symptom diagnostic table.

•	Hard Start

•	Surges/Chuggles

•	Lack of Power, Sluggishness, or Sponginess

•	Detonation/Spark Knock

•	Hesitation, Sag, Stumble

•	Cuts Out, Misses

•	Poor Fuel Economy

•	Poor Fuel Fill Quality

•	Rough, Unstable, or Incorrect Idle and Stalling

•	Dieseling, Run-On

•	Backfire

System OK

Go to Intermittent Conditions