Symptoms - Engine Controls

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Important Preliminary Checks

Important Preliminary Checks	Action
Before performing Symptom diagnosis	Before performing Symptom based diagnosis you must perform the Diagnostic System Check - Alternative Fuels (Engine Controls) . The System Check will determine the following: The FICM, PCM and the MIL are operating correctly. There are no DTCs stored. Scan tool data is within normal operating range. Several of the Symptom diagnostic tables require that a Visual and Physical Check be performed. Always perform a Visual and Physical Check before using a Symptom diagnostic table.
Visual and Physical Checks	Inspect the FICM and PCM ground connections for being clean, tight and in the correct location. Inspect the PCM for the correct CNG calibration. Program the PCM if necessary. Inspect the vacuum hoses for leaks, restrictions and proper connection as shown on the vehicle emission control information (VECI) label. Inspect for any type of fuel leak or fuel line restriction. Inspect for air leaks at all areas of the intake manifold sealing surfaces. Inspect the ignition wires for the following conditions: Cracking Hardness Proper routing Carbon tracking Inspect vehicle wiring for the following: Proper connection Pinches Cuts
Symptoms	Verify the customer concern. Locate the Symptom table that indicates the customers concern. Test or Inspect for the items indicated for that symptom. The following Symptom tables are located in this section: Intermittent Conditions Hard Start Surges/Chuggles Lack of Power, Sluggishness, or Sponginess Hesitation, Sag, Stumble Cuts Out, Misses Poor Fuel Economy Poor Fuel Fill Quality Rough, Unstable, or Incorrect Idle and Stalling Dieseling, Run-On Backfire

Action

Before performing Symptom diagnosis

Before performing Symptom based diagnosis you must perform the Diagnostic System Check - Alternative Fuels (Engine Controls) .
The System Check will determine the following:

The FICM, PCM and the MIL are operating correctly.
There are no DTCs stored.
Scan tool data is within normal operating range.

Several of the Symptom diagnostic tables require that a Visual and Physical Check be performed. Always perform a Visual and Physical Check before using a Symptom diagnostic table.

Visual and Physical Checks

Inspect the FICM and PCM ground connections for being clean, tight and in the correct location.
Inspect the PCM for the correct CNG calibration. Program the PCM if necessary.
Inspect the vacuum hoses for leaks, restrictions and proper connection as shown on the vehicle emission control information (VECI) label.
Inspect for any type of fuel leak or fuel line restriction.
Inspect for air leaks at all areas of the intake manifold sealing surfaces.
Inspect the ignition wires for the following conditions:
- Cracking
- Hardness
- Proper routing
- Carbon tracking
Inspect vehicle wiring for the following:
- Proper connection
- Pinches
- Cuts

Symptoms

Verify the customer concern.
Locate the Symptom table that indicates the customers concern.
Test or Inspect for the items indicated for that symptom.

The following Symptom tables are located in this section: