Two of our long-time customers brought in their 2005 Acura MDX because it had an engine oil leak on the right side. They were going to take a long trip and wanted to make sure everything was OK. We lifted the car and checked for the leak and found that the engine oil pump was leaking. Unfortunately, this oil pump sits behind the timing belt and on top of the engine oil pan. The timing belt and oil pan have to be removed to perform the job properly. The couple decided to leave the car, and we got on it right away.
Side note: If you own a 2003 to 2018 Honda or Acura with a 3.5-liter timing belt motor, the engine oil pump should always be checked for an engine oil leak before performing a timing belt.
We performed the engine oil pump, timing belt and engine oil pan reseal. The customers picked up the car and left for their trip. During the trip, they drove 850 miles without any drivability problems. Halfway through the trip, they stopped to refuel. After refueling, they noticed that the check engine light was on. Halfway home, the check engine light turned off. Upon returning, the husband pulled a code with their generic scan tool. The code was a P0706 transmission range switch signal performance. The moment he told me the code, it piqued my interest. This code was highly unusual for an Acura.
The primary purpose of the transmission range position switch is to communicate to the engine control module the position of the transmission shifter. Technically, it is a safety device, so the engine cannot be started with the transmission in drive or reverse. The switch also illuminates the selector lights in the instrument cluster (P,R,N,D,1,2,3). The switch also commands the backup lights.
Once the car was in the shop, we connected our scan tool and pulled the same code. We then disconnected the switch and tested the connector. The connector on the car side checked out OK. We then started testing the switch. We found that one of the pins had extremely high resistance. At that point, we knew we had to change the switch.
Now, you are probably wondering why I’m writing an article that starts off with an oil leak, then an oil pump repair and then a check engine light. The reason is that the failure of this range switch was so rare that I thought it was going to be an onboard diagnostic (OBD) mistake. Also, because after 36 years of working on Acuras, I had never replaced a range switch on an MDX. I thought for sure it was going to be something strange, like rodent damage or water intrusion.
The other interesting thing was that the range switch was nowhere to be found. Acura has the range switch on back order with no estimated time of arrival. When I called my local Acura dealer, they stated that they had zero history of ever selling the part. After that, I had my local Acura dealership check the inventory in all other Acura dealerships in the U.S. The locator showed only two. After contacting the first dealership, I was informed that the inventory was incorrect, and they did not have one. Luckily, the last dealership I called had one in stock. The only one in North America. We ordered the part and got ready to install it.
Before installing it, we did a side-by-side test of the old switch and the new switch just to double-check our diagnostic. The side-by-side check confirmed our diagnosis was correct. We replaced the part, performed the adjustments and test drove the car.
In the end, the range switch was not causing the car to have any driveability problems and had nothing to do with any of the previous work. Yet if left alone, it may have eventually caused a shifting problem or may have caused the car not to start.
Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call (650) 960- 6988, email [email protected] or visit sunnyvaleforeigncar.com.
