Express 1500 RWD V8-5.3L (2008)
Temperature Sensitivity
*
An intermittent condition may occur when a component/connection reaches normal operating temperature. The condition may occur only when the
component/connection is cold, or only when the component/connection is hot.
*
Freeze Frame, Failure Records, Snapshot, or Vehicle Data Recorder data may help with this type of intermittent condition, where applicable.
*
If the intermittent is related to heat, review the data for a relationship with the following:
-
High ambient temperatures
-
Underhood/engine generated heat
-
Circuit generated heat due to a poor connection, or high electrical load
-
Higher than normal load conditions, towing, etc.
*
If the intermittent is related to cold, review the data for the following:
-
Low ambient temperatures-In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion.
-
The condition only occurs on a cold start.
-
The condition goes away when the vehicle warms up.
*
Information from the customer may help to determine if the trouble follows a pattern that is temperature related.
*
If temperature is suspected of causing an intermittent fault condition, attempt to duplicate the condition. Refer to Inducing Intermittent Fault
Conditions in order to duplicate the conditions required. See: Testing and Inspection/Component Tests and General Diagnostics
Electromagnetic Interference (EMI) and Electrical Noise
Some electrical components/circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following
conditions:
*
A misrouted harness that is too close to high voltage/high current devices such as secondary ignition components, motors, generator etc-These
components may induce electrical noise on a circuit that could interfere with normal circuit operation.
*
Electrical system interference caused by a malfunctioning relay, or a control module driven solenoid or switch-These conditions can cause a sharp
electrical surge. Normally, the condition will occur when the malfunctioning component is operating.
*
Improper installation of non-factory or aftermarket add on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters,
alarm systems, cell phones, etc-These accessories may lead to interference while in use, but do not fail when the accessories are not in use. Refer
to Checking Aftermarket Accessories. See: Testing and Inspection/Component Tests and General Diagnostics
*
Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
*
The generator may be allowing AC noise into the electrical system.
Incorrect Control Module
*
There are only a few situations where reprogramming a control module is appropriate:
-
A new service control module is installed.
-
A control module from another vehicle is installed.
-
Revised software/calibration files have been released for this vehicle.
Important: DO NOT re-program the control module with the SAME software/calibration files that are already present in the control
module. This is not an effective repair for any type of concern.
*
Verify that the control module contains the correct software/calibration. If incorrect programming is found, reprogram the control module with the
most current software/calibration.
Testing for Short to Ground
Testing for Short to Ground
Notice: Refer to Test Probe Notice.
The following procedures test for a short to ground in a circuit.
With a DMM
1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
2. Disconnect the load.
3. Set the rotary dial of the DMM to the ohm position.
4. Connect one lead of the DMM to one end of the circuit to be tested.
