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"Hybrid Vehicle Issues And Fixes"

April 26, 2019

2008 Ford Escape with 110K on the odometer. It had a bunch of problems preventing it for being driven to our shop. We got this vehicle through a recommendation from John Anello, also known as the AutoTech On Wheels. He had diagnosed a no-start issue for the Escape owner, who had the vehicle towed from New Jersey to our shop in New York based on John's referral.

 

The first thing I checked was the HV inertia switch since the vehicle had a no start condition. I found the inertia switch in the normal state and also found the shut off/service plug installed correctly. Since they were both in their normal state, my next step was to perform a visual inspection of the remaining HV components. I followed that up with connecting the Ford IDS scan tool to check for DTCs and PID information.

 

The scan data revealed over eleven DTCs (Figure 5) but the one that attracted my immediate attention was a P0AA6-60 (High Voltage System Isolation Fault) DTC. This was the main cause of the no start condition. When you encounter a hybrid vehicle that displays an isolation fault, you could be in for big problems. Since this Ford Escape does not have an electric air conditioning compressor I could rule out the isolation fault being caused by an A/C compressor that had been contaminated with PAG oil. My next step was to look at scan data for the HV battery and see if the scan tool data would reveal anything else besides the P0AA6-60 DTC.

 

I found that the HV battery pack (Figure 6) was at a 0 percent and R_LeakN and R_Leak P at 1 Mohm of resistance that was off the scale indicated by a blue dot at the right side of the data PID. The battery pack voltage was down to 247.13 volts, very low since it should be somewhere in the 300 volt SOC (State Of Charge) range. The average SOC at 0 percent, but yet the BathPac_Stat stated OK along with one CCNT_BCM DTC. I now knew this was going to be a big mess after reviewing the scan tool data. I had never come across a Ford Escape hybrid with so many issues. Ford took their time making sure they built a robust hybrid, so they could launch their way into the hybrid business. I should also state that this is a second generation Escape hybrid that if anything was an improvement over the Gen 1 models.

 

With my work cut out for me I started with the service disconnect fuse (Figure 7) that I checked carefully, discovering an issue with it. Looking at the fuse I notice it had a black stain on the white band that I had never seen before. Knowing that the fuse condition was not normal even though it had continuity, I knew there had to be something that caused this issue, such as low electrical resistance that caused too much current flow. I moved the service plug disconnect in to the Service Shipping position then proceeded to remove the HV wires from the right side of the HV battery pack. I followed that up by removing the HV wire connector from the motor generator that is located under the air filter box on the left front of the vehicle.

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