- Symptoms - Engine Controls

SYMPTOMS - COMPUTERS AND CONTROL SYSTEMS

IMPORTANT PRELIMINARY INSPECTIONS BEFORE STARTING
Before using the Symptom tables, perform the following:
- Perform Diagnostic System Check - Vehicle and verify all of the following items:
- Ensure that the engine control module (ECM) and malfunction indicator lamp (MIL) are operating correctly.
- Ensure that there are no diagnostic trouble codes (DTCs) that are stored.
- Scan tool data is within a normal operating range. Refer to Scan Tool Data List. Scan Tool Data List Testing and Inspection
- Verify the customer concern.
- Perform the Visual/Physical Inspection. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
- Locate the correct symptom. Perform the tests and inspections associated with the symptom.

IDENTIFYING INTERMITTENT CONDITIONS
Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition:
- Moisture and water intrusion in connectors, terminals, and components
- Connector mating
- Terminal contact
- High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
- Harness that is located too tight, or chaffed circuits
- High or low ambient temperature
- High or low engine coolant temperatures
- High underhood temperatures
- Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load
- High or low system voltage
- High vehicle load conditions
- Rough road surface
- Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
- Incorrect installation of non-factory, aftermarket, and after factory add on accessories

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions. Component Tests and General Diagnostics

VISUAL/PHYSICAL CHECK

NOTE: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:
- The PCM harness connectors
- The electrical center fuse/relay cavities
- The component terminals
- The component harness connector

Using this kit will prevent damage caused by the improper probing of connector terminals.

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 time. This inspection should include the following areas:
- Ensure that the control module grounds are clean, tight, and correctly located.
- Inspect vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of a leak or a restriction.
- Inspect for a dirty or restricted air filter.
- Inspect for water intrusion in the mass air flow (MAF)/intake air temperature (IAT) sensor connector, heated oxygen sensor (HO2S) connectors, control module connectors or any other harness connectors.
- Inspect the air intake ducts, particularly between the MAF sensor and the throttle body for the following conditions:
- Collapsed
- Damaged areas
- Looseness
- Incorrect installation
- Leaking
- Inspect for air leaks at the throttle body mounting area, the MAF sensor and intake manifold sealing surfaces.
- Inspect the wiring harness for the following conditions:
- Poor connections
- Pinches
- Cuts
- Inspect for loose, damaged, unseated, or missing sensors/components.
- Inspect terminals for corrosion and correct contact.
- 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