GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2004 🢒 Isuzu - N Series 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L80-E/4L85-E 🢒 Diagnostic System Check - 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.

  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. This step stores the powertrain control module (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/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 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

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

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. • Powertrain control module (PCM)
    • Body control module (BCM)
    • Instrument panel (IP) cluster
    • 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

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:

    • PCM
    • BCM
    • IP Cluster
    • EBCM
    • DIC
    • HVAC

Does the scan tool display any DTCs?

Go to Step 5

Go to Step 9

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 DTC List in Data Link Communications

Go to Step 7

7

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

Go to DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

Go to Step 8

8

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

Go to DTC List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List

9

Is the customer's concern with the automatic transmission?

Go toDiagnostic System Check in Automatic Transmission

Go to Step 10

10

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

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

Go to Step 11

11
  1. Review the following symptoms.
  2. Refer to the applicable symptom diagnostic table:
    3. •  Hard Start
    •  Backfire

Did you find and correct the condition?

System OK

Go to Intermittent Conditions