Electromagnetic Interference & Electrical Noise
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
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, Powertrain Control Module (PCM) driven solenoid or switch. These conditions can cause a sharp electrical surge. Normally, the condition occurs 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 an emission related OBD II failure while in use, but do not fail when the accessories are not in use. If a DTC is determined to be intermittent, and the tests in this section do not reveal a condition, go to VEHICLE DATA RECORDER later in this table.
- Check for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
- Check the generator for a bad rectifier bridge that may be allowing AC noise into the electrical system.