Tech Tip: Rust and Corrosion May Be Culprit When Signs Point to Faulty DIS Modules

Tech Tip: Rust and Corrosion May Be Culprit When Signs Point to Faulty DIS Modules

A vehicle towed into a shop is a "no start." Preliminary troubleshooting leads a technician to suspect the culprit may be a faulty DIS (Distributorless Ignition System) module. So the module is bench tested using the ignition module tester, but the results show the component seems to be working fine. The DIS module is placed back on the vehicle and the troubleshooting continues.

It’s a common problem that may have a simple solution.

A vehicle towed into a shop is a “no start.” Preliminary troubleshooting leads a technician to suspect the culprit may be a faulty DIS (Distributorless Ignition System) module. So the module is bench tested using the ignition module tester, but the results show the component seems to be working fine. The DIS module is placed back on the vehicle and the troubleshooting continues.

Unfortunately, the problem may have just been overlooked.

“Technicians will put the module back on the vehicle and spend additional diagnostic time looking elsewhere for the problem because the module passed,” said Don Josefik, BWD manager of training and support operations. “We need to take a look at the DIS module ground-corrosion issue and address the solutions.”

The ground-corrosion issue Josefik refers to deals with DIS modules that use their mounting plate for the ground circuit. In time, rust and corrosion can build up on the metal plate and mounting bracket on the vehicle, which can lead to a bad module ground. When the ground to the module is lost, the module will not function, in turn causing no spark or fuel injector pulses.

Not all modules use their mounting plate for the ground. In some applications, the ground circuit is one of the pins in the module’s connector. In those applications, this tip does not apply.

When performing a module test, a good way of determining if the module’s mounting plate is also the ground is to note whether the tester’s adapter for the module being tested has a separate alligator ground clip. If it does, then the module’s mounting plate is also the ground.

“What can happen is the person performing the test will put the ground clip on a clean area of the metal plate,” Josefik said, “run the test and get a passing result because the module has a good ground.”

Josefik said if rust or corrosion is found on the module and the test is a pass, the technician must be advised to clean the module’s metal plate and the module-mounting bracket with sand paper, wire brush or other suitable means. The metal of both the bracket and the module must be completely clean and free from any rust or corrosion.

Courtesy of BWD Automotive

For additional information on BWD Automotive and the products they offer, visit www.bwdautomotive.com.

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