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 in the diagnostic table.

1. Lack of communication may be due to a malfunction of the serial data circuit, the control module, or the scan tool. The specified procedures in Data Link Communications will determine the particular condition.

2. This step stores the powertrain control module (PCM) DTC information into the scan tool 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. 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:

• | When you are instructed to clear the DTCs.

• | The PCM connectors are disconnected.

• | The PCM is replaced during a diagnostic procedure or a repair procedure.

3. A DTC P0601 that is stored must be diagnosed first. If multiple powertrain DTCs are stored, diagnose in the following order of priority:

• | 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.

4. This step is for vehicles that are located in 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
--- | --- | --- | ---
1 | 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 Starting Point - Engine Electrical .

• | Ensure the battery is fully charged.

• | Ensure the battery cables are clean and tight.

• | Ensure the powertrain control module (PCM) grounds are clean, tight, and in the proper location.

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 powertrain control module (PCM).

Does the scan tool communicate with PCM?

Go to Step 3

Go to Scan Tool Does Not Communicate with Vehicle Control Module/Powertrain Control Module 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 Information on the scan tool. Does the scan tool display any Powertrain DTCs? | Go to Step 5 | Go to Step 7
5 | With the 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 DTC P0601? | Go to DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 | Go to Diagnostic Trouble Code (DTC) List Engine Controls
7 | Is the customer's concern with Inspection/Maintenance (I/M) testing? | Go to Inspection/Maintenance (I/M) System Check | Go to Step 8
8 | Perform the applicable symptom 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

• | Malfunction Indicator Lamp (MIL) Inoperative

• | Malfunction Indicator Lamp (MIL) Always On

Did you find and correct the condition?

System OK

Go to Intermittent Conditions