For 1990-2009 cars

### 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 PCM 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 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

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. 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

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 powertrain control module (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:

• | PCM

• | 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

• | EBCM

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 Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Step 7
7 | Does the scan tool display DTCs P0601, P0602, P0604, P0606, or P1683? | 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 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 Automatic Transmission-Allison | Go to Step 10
10 |

1. Review the following symptoms.
2. 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

• | Rough, Unstable, or Incorrect Idle and Stalling

• | Dieseling, Run-On

• | Backfire

Did you find and correct the condition?

System OK

Go to Intermittent Conditions