Diagnostic System Check - Alternative Fuels (Engine Controls). GMC Truck Savana (CNG) 2004

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 Savana (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 Diagnostic System Check - Alternative Fuels (Engine Controls)

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.

The bi-fuel (KL6) vehicle and the dedicated CNG (KL8) vehicle require unique fuel injector control modules. DTC U0306 sets when the PCM detects an incorrect FICM has been installed for the vehicle application.

This step determines if the vehicle will start.

This step stores the powertrain control module (PCM) diagnostic trouble code (DTC) information into the scan tools 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/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 determines if the vehicle will operate on the gasoline fuel system.

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.

Engine Controls Diagnostic System Check

Step

Action

Yes

Important:

•	DO NOT perform this test if no driveability condition exists.

•	Search for applicable bulletins before proceeding with the diagnosis.

•	DO NOT turn OFF the ignition when performing this diagnostic table.

•	DO NOT clear the DTCs unless the diagnostic instructs you to do so.

•	If there is a condition with the starter system, refer to Diagnostic System Check - Engine Electrical in Engine Electrical in the G/H Van Service Manual.

•	Ensure the battery is fully charged and the cables are clean and tight.

•	Ensure the PCM and the fuel injector control module (FICM) grounds are clean, tight, and in the proper location.

•	Ensure the CNG and the gasoline fuel tanks are at least ½ full.

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 in the G/H Van Service Manual

Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information with the Class 2 Message Monitor feature:

•	Powertrain control module (PCM)

•	Body control module (BCM)

•	Instrument panel cluster (IPC)

•	Electronic brake control module (EBCM)

•	Driver information center (DIC)

•	Heating ventilation air conditioning (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 in the G/H Van Service Manual

Select the DTC display function for the PCM.

Does the scan tool display DTC U0306?

Go to Fuel Injector Control Module Replacement

Go to Step 4

Attempt to start the engine.

Does the engine start and idle?

Go to Step 5

Go to DTC P1204

Select the DTC display function for the following control modules:

•

BCM

•

IPC

•

EBCM

•

HVAC

Does the scan tool display any DTCs?

Go to Step 6

Go to Step 11

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" except U0306?

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications in the G/H Van Service Manual

Go to Step 8

Were any of the PCM DTCs P0601, P0602, or P1621 set?

Go to DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 in Engine Controls in the G/H Van Service Manual

Go to Step 9

Is DTC P0611 set?

Go to DTC P0611

Go to Step 10

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

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical in the G/H Van Service Manual

Go to Diagnostic Trouble Code (DTC) List

Is the vehicle equipped with the dedicated CNG fuel option (KL8)?

Go to Step 13

Go to Step 12

Start and idle the engine.
Force a switch over to gasoline operation with the scan tool in the Alternative Fuels special functions, output controls menu.

Does the engine continue to idle?

Go to Step 13

Go to Engine Cranks but Does Not Run in the G/H Van Service Manual

Is the customer's concern with the Transmission?

Go to Diagnostic System Check - Automatic Transmission 4L80-E in Automatic Transmission in the G/H Van Service Manual

Go to Step 14

Is the customer's concern with the inspection/maintenance (I/M) testing?

Go to Inspection/Maintenance (I/M) System Check in Engine Controls in the G/H Van Service Manual

Go to Step 15

If the customer's concern is a symptom, refer to Symptoms - Engine Controls

Did you find and correct the condition?

System OK

Go to Intermittent Conditions