“It’s going to be something simple, I’m sure,” Walter said, regarding a 2009 Acadia with a steering problem. The Acadia has a variable effort steering system that controls the amount of effort to steer the Acadia with changes in lateral acceleration and wheel speed.

“We replaced the actuator already,” Walter said.

The actuator is in the steering rack and pinion, a simple pintle valve and electromagnetic coil. The EBCM controls the actuator from a range of about 0-to-1-amp. Amperage goes down as vehicle speed goes up.

“We replaced the EBCM and it didn’t make any difference. How much is all this gonna cost me?” Walter asked.

“More than a little, less than a lot,” I said.

The EBCM uses the steering wheel position sensor input to calculate lateral acceleration during hard maneuvers.

“We replaced the steering wheel position sensor,” Walter said. “There is also a Service Steering System warning message on the dash.”

I already did my preliminary checks prior to visiting Walter’s facility. He said an upgraded radio was installed, a factory install. “The problems started after the upgraded radio was installed,” Walter said.

There were no TSBs or PI documents, and I unplugged the cell phone charger. I verified the concern and checked all fuses.

“We checked all the fuses and they’re fine.”

“Well, I’m checking them again,” I replied.

I checked the terminals at the EBCM, inspecting them with my magnifier.

“We did all that,” he said.

“Good—and so am I,” I said.

I checked the EBCM ground. Walter shook his head. “We did all that, Bob—you don’t know what’s wrong, do you?”

“No, not yet,” I said. I began doing a thorough visual inspection, looking for anything unusual. Sometimes rodent intrusion takes a toll.

“You won’t find anything,” Walter said.

It was getting kind of irritating.

I plugged in my Tech 2 to check communication with the modules. The ECM, Headlamp Control Module, the Vehicle Communication Interface Module, the EBCM, the Fuel Pump Control Module, and the Rear Diff Clutch Control Module were all communicating. The ABS lamp and the Red Brake Warning Lamp were illuminated. Several history U-codes but two current DTC’s were stored.

DTC C0450 5A:  Steering Assist Control Solenoid Actuator Circuit plausibility failure, and DTC C0450 00:  Steering Assist Control Solenoid Actuator Circuit.

The EBCM controls power to the actuator through a high side driver. Walter checked it with a test light while commanding the actuator on and off, and the test light glows. But on the ground side, the test light did not illuminate.

“Maybe the new EBCM is bad,” Walter suggested.

“You can’t check the GFET with a test light,” I said. This is how you check it, according to the service manual:

1. Connect a DMM, set on the diode setting, between the low control circuit terminal 1 and ground.
2. Command the VES actuator to 0% with a scan tool. The DMM reading should be greater than 2.5 volts or display O.L.

⇒X	If less than the specified value, test the low control circuit for a short to voltage or a short to ground. If the circuit tests normal, replace the EBCM.

3. Command the VES actuator to 100% with a scan tool. The DMM reading should be less than 1 volt.

⇒X	If greater than the specified range, test the low control circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.

4. If all circuits test normal, test or replace the VES actuator.

 

We checked the GFET with my Fluke meter on diode test and it passed.

“So, we do have another bad EBCM,” Walter said. “I also checked the wires with an ohm meter and they were good. It must be a bad EBCM.”

I focused on the wires going to the EVO actuator. Using my load tester, I found that the ground side leading from the GFET in the EBCM could not support a load. Closer inspection revealed some broken strands under the insulation not far from the actuator.

This was a misleading one because the problem apparently occurred shortly after a new radio was installed. That was merely a coincidence in this case. As far as the U-codes, maybe they flagged when the radio was replaced and the dealership didn’t bother to clear them.

“That’s all it was—a broken ground wire? And you’re going to charge me for a broken wire?”

“No, Walter—I repaired the wire for free. I charged you for my diagnostic time. That’s all I ever charge for.”

Walter settled down after a bit. He apologized for acting like a typical customer.