GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Regal 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Diagnostic System Check - Engine Controls

Description

The Diagnostic System Check is an organized approach to identifying a condition created by an electronic engine control system malfunction. 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 diagnosing the concern. Understanding the table and using the table correctly 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 due to a partial malfunction of the class 2 serial data circuit or due to 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) diagnostic trouble code (DTC) information into the scan tools memory. Review the captured information at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored. It is beneficial to review the Freeze Frame/Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information and other operating conditions when the DTC set may help diagnose an intermittent condition. Capturing the stored information preserves data that the PCM loses when the following occurs:

    3. • When you are instructed to clear DTCs.
    • The PCM connectors are disconnected.
    • The PCM is replaced during a diagnostic procedure.

  3. The presence of DTCs which begin with --U-- indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

    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 multiple powertrain DTCs are stored, diagnose in the following order of priority:

    5. • Component level DTCs--Sensors, solenoids, relays etc. Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC, unless otherwise directed.
    • System level DTCs--Misfire, fuel trim, catalyst etc.

  5. This step is for areas that have an Inspection/Maintenance or emission testing program. The testing facility found one or more I/M system statuses not set.

A Diagnostic System Check Engine Controls

Step

Action

Yes

No

Important: 

   • DO NOT perform this diagnostic if no driveability condition exists, unless directed from another procedure.
   • Search for applicable service bulletins before proceeding with diagnosis.
   • DO NOT clear DTCs unless instructed by a diagnostic procedure.
   • If there is a condition with the starting system, refer to Diagnostic System Check - Engine Electrical .
   • Ensure the battery is fully charged.
   • Ensure the battery cables are clean and tight.
   • Ensure the PCM grounds are clean, tight, and in the proper location.

1

Install a scan tool.

Does the scan tool power-up?

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. • PCM
    • Body control module (BCM)
    • Instrument panel cluster (IPC)
    • HVAC (CJ2)
    • Electronic brake control module (EBCM)

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
    • IPC
    • HVAC (CJ2)
    • EBCM

Does the scan tool display any DTCs?

Go to Step 5

Go to Step 9

5

With a scan tool, save or capture the Powertrain DTC information, Store Information.

Did you complete the action?

Go to Step 6

--

6

Does the scan tool display any 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 P0601 or P0602?

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 DTC P0560?

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

Go to Diagnostic Trouble Code (DTC) List

9

Is the customer's concern with the automatic transmission?

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

Go to Step 10

10

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

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

Go to Step 11

11
  1. Review the symptoms listed below.
  2. Perform the applicable symptom table:
    3. •  Hard Start
    •  Backfire

Did you find and correct the condition?

System OK

Go to Intermittent Conditions