The Malibu Mystery Solved

Remember the Malibu from the previous post with the intermittent stalling? The shop could only duplicate the concern once and every time they checked the ETC fuse with a test light, it checked out okay. They replaced the engine controller as a possible cause after thoroughly checking the wiring and grounds.

The fuse was the common denominator to the two fault codes, remember? I told them that they kept checking the fuse with a test light, on both sides of the fuse.

“Correct,” Al said, “we followed the service procedure, key on, engine off, while checking the ETC fuse. We even checked it with a digital meter.”

“That was fine, Al—but why not check the fuse under the conditions that the customer reported the concern? The engine was running when it intermittently stalled. How about checking the fuse with the engine running?”

While I waited on the phone, Al made the check.

“Jack—when I checked the fuse with the engine idling, the engine stalled and started up in reduced power mode. Did the test light load the fuse or something?”

“Or something,” I said. “Clear the codes, start the engine and then press on the fuse with your finger.”

As soon as Al did, the engine stalled. You guessed it—the circuit board in the fuse box, or Power Distribution Center, or Underhood Bussed Electrical Center, as some manufacturers call it—had a fracture. The fuse box has to operate in very grueling conditions when in the engine compartment—temperature, vibration—and they can fail.

I just received an email from another shop with a C4500 Medium Duty truck “eating” heater cores for breakfast. Coolant was changed, system flushed, measured voltage in the radiator was 100 millivolts. They had installed a ground strap on the heater core but it makes no difference.

But, HiTech Investigations is closed for now. Until next time, this is Jack McGinnis, signing off and putting my notepad away.

Thanks for reading and happy hunting!