Symptoms - Engine Controls

Symptoms - Computers and Control Systems

Important: Preliminary Checks Before Starting

Before using the Symptom tables use the following:

* Perform Diagnostic System Check - Vehicle and verify all of the following items: Initial Inspection and Diagnostic Overview

- Ensure no DTCs are stored.
- Check that the scan tool data is within normal operating range. Refer to Scan Tool Data List. Scan Tool Data List

* Verify the customer complaint.
* Perform the Visual/Physical Check.

Locate the correct symptom in the list at the end of this section. Follow the procedures in the appropriate diagnostic table. If the condition cannot be duplicated or is determined to be intermittent, refer to Intermittent Conditions. Intermittent Conditions

Visual/Physical Check

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save valuable time. This inspection should include the following areas:

* Inspect the powertrain control module (PCM) grounds for being clean, tight, and in their proper location.
* Inspect vacuum hoses for splits, kinks, and proper connections, as shown on Vehicle Emission Control Information label. Inspect thoroughly for any type of leak or restriction.
* Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking, especially between the mass air flow (MAF) sensor and the throttle body.
* Inspect for air leaks at throttle body mounting area, MAF sensor and intake manifold sealing surfaces.
* Inspect the wiring harness for poor connections, pinches, cuts, or other damage.
* Inspect for loose, damaged, or missing sensors and/or components.

Use the following tables when diagnosing a symptom complaint:

* Intermittent Conditions
* 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
* Malfunction Indicator Lamp (MIL) Inoperative
* Malfunction Indicator Lamp (MIL) Always On
* Engine Cranks but Does Not Run