- Symptoms - Engine Controls

Symptoms - Computers and Control Systems

Important Preliminary Checks

Before Starting

Before using this section, perform the Diagnostic System Check - Vehicle and determined that the following items are OK:

* The control module, malfunction indicator lamp (MIL), and check engine are operating correctly.
* There are no DTCs stored.
* The scan tool data is within normal operating range. Refer to Scan Tool Data List. Initial Inspection and Diagnostic Overview Scan Tool Data List

Verify the customer complaint, and locate the correct symptom in the table of contents. Inspect the items indicated under that symptom.

Visual/Physical Check

Several of the symptom procedures call for a careful visual/physical check. The importance of this step cannot be stressed strongly enough. This step can lead to correcting a condition without further inspections and can save valuable time. This inspection should include:

* Control module grounds for the following conditions:

- A clean connection
- A tight connection
- Proper location
Refer to Power and Grounding Component Views.

* Vacuum hoses for the following conditions:

- Splits
- Kinks
- Proper connections as shown on the Vehicle Emission Control Information label-Refer to Emission Hose Routing Diagram.
- Leaks
- Restrictions

* Air leaks at the following components:

- Throttle body mounting
- Intake manifold sealing surfaces

* Wiring for the following conditions:

- Proper locations
- Pinches
- Cuts

* Use the following tables when diagnosing a symptom complaint:

- Hard Start
- Surges/Chuggles
- Lack of Power, Sluggishness, or Sponginess
- Detonation/Spark Knock
- Hesitation, Sag, Stumble
- Cuts Out, Misses
- Poor Fuel Economy
- Poor Fuel Fill Quality
- Rough, Unstable, or Incorrect Idle and Stalling
- Dieseling, Run-On
- Backfire