The Case of The Puzzling Enclave

 

 

While driving home on I-70 at Dallas Pike, I stopped for supper at a TA facility of Exit 11. I was headed back from an interesting diagnostic investigation in Pennsylvania and encountered another in the parking lot. A technician was working on a 2011 Buick Enclave and I decided to join her.

"What's up?" I asked, watching her read the data with a scan tool.

She mentioned that she was from a shop west of the truck stop and was taking the Enclave on a road test. "Do you know anything about diagnosing vehicles?"

"Just a little," I told the young technician."

"The Money Indicator Light turns on intermittently," Helen said, "And there is a P069E that sets in the ECM and a P2534 in the Fuel Pump Control Module. The vehicle came in for an oil change and tire rotation. Less than a month later the customer brought it back for this. The FPCM was replaced twice."

"At least you know what it isn't," I said. I couldn't resist. Helen didn't seem to appreciate it.

"There are no aftermarket components on it," Helen said.

I knew that the FPCM got the commanded fuel pressure message from the engine controller and the FPCM sends a PWM signal to the fuel pump. Pump speed was changed by varying the signal's duty cycle. Helen was prepared. Wiring diagrams and diagnostic charts were on the passenger seat.

"If there are codes set in the FPCM, then the FPCM will request the PCM to set a P069E," she said. "And since the P069E is an information only code, I did not change the FPCM because of it," she added. "But the other code--the P2534--sets if the ignition is less than six volts on the pink wire going in to the FPCM."

"That would be circuit number 439," I said.

"Right--an every time I tested it at the FPCM connector, referenced to ground, it read about 12.47 volts."

"That sounds normal," I said.

"And the service information stated that if all circuits tested normal, the FPCM should be replaced. I replaced it and programmed the new module but P069E returned as an active fault in the PCM and P2534 returned as an active code in the FPCM," Helen said.

"There is a free website where you can enter the VIN and---" She interrupted me.

"Been there, done that," she said. "I also checked the Safercar.gov website and ran a VIN search with no results."

Helen was thorough. I estimated that she was in her early twenties, so she didn't have much experience; but she was thorough. "Did you attend a technical college?" I asked.

"Yes, back in Pennsylvania. I graduated the highest in the class," She said with pride.

"It shows," I said. "I've got a factory tool in my car--how about we try it on this vehicle?"

"You've got a Tech2?"

She even knew the name of the old GM factory scan tool. "I'll be right back."

I gave the Tech2 to her to use. To my utter amazement, Helen pushed the buttons on the Tech2 so fast that her fingers were a blur.

"Wow--I take it you've used it before?"

"No, this is the first time I've had one in my hands."

"Then how can you push the buttons faster that I could ever hope for?"

"Are you kidding? Video games are my life when I'm not in the shop. I don't know what I'm looking for but I can move through all the menus pretty easily," she said.

"Go to the FPCM Data List," I told her. She was there before I could take in another breath. I spotted a data PID that wasn't right. "The Ignition 1 voltage is indicating zero volts," I said.

That was Circuit #439, Pin #11, at the FPCM.

"It should be battery power, right?" Helen asked.

"Right," I said.

Helen grabbed a voltmeter, crawled under the rear of the vehicle, and accessed the connector to the FPCM. "I'm reading 12.51 volts at pin #11, she said.

That didn't make sense. The data PID on the scan tool indicated zero volts but the pin at the connector read battery voltage, what it should be. Yet the FPCM saw nothing. Service information indicated a new FPCM was needed.

"We need to check one more thing," I said.