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Did a rear impact or a rodent cause this engine problem?

Friday, May 4, 2018 - 07:00
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I was called to a body shop with a hard start and CEL lamp illumination on a 2013 Toyota Sienna with a 3.5 Liter engine (Figure 1) that was recently involved in a rear-end collision. The vehicle had been in the shop for quite a while due to extensive repairs. The car was finally finished but it was hard for the shop to know for sure if this issue was caused by the impact or whether it was a preexisting problem. It is not uncommon for a vehicle to be involved in an accident and having multiple post problems that may be unrelated to a claim. It is up to the shop and the insurance company to question the owner of the vehicle to see who is actually liable for problems that may seem unrelated. 

Figure 1

It is so important prior to working on a vehicle to take many pictures of the vehicle damage to build a case for a claim. What is also important, if the vehicle runs, is to take a picture of any warning lights on the dash. These indicator lights will usually illuminate if there are any underlying problems that you may not be able to see. It is also a good idea to perform a full vehicle scan using a scan tool to get a better evaluation of unforeseen issues with a vehicle. Most of the scan tools out there today can actually print out a report that you can place in a folder that can help build your claim. 

Keep in mind that there may be error codes stored on that report that could have been set prior to the accident and may not be related to the claim. It is up to a good body technician who has some scan tool experience to evaluate each and every code to see which ones hold value and if they are related. There are usually present or past codes stored in a vehicle. The past codes could have been in memory for quite a while and even before the accident took place. The present codes are the ones you need to address. These are the codes that will keep warning lights on and will only come back once they are cleared so they need to be addressed in order to complete the vehicle for delivery back to the owner. Remember that it’s all about customer satisfaction and shop ratings. 

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I proceeded to hook up my scan tool and performed a vehicle scan. There was only one code stored in the engine computer, but there were no codes stored in any of the other controllers. This was because the shop tried to clear all vehicles codes by disconnecting the vehicle battery cables. This is usually not a good practice because if you disconnect a battery rather than clear the entire vehicle with a proper scan tool, you will run the chance of losing vehicle-learned procedures of many system components on board. This could include learned calibrations for Steering Angle Sensor Positioning, Occupant Seat Weight, Headlight Positioning, Camera Positioning, Power Window Pinch Limits and much more.  

Figure 2

When I did clear the engine controller, the Check Engine light kept returning with a present code P0118 for a coolant sensor circuit high input (Figure 2). The coolant sensor was a two-wire sensor screwed into the engine coolant passage that was feeding a 5 Volt reference and a ground reference. The sensor itself was a negative coefficient thermistor whose resistance lowers as engine temperature rises. This code indicated either an open circuit in either of the feed wires or a bad coolant sensor with abnormally high resistance.  

Figure 3

At this point it was easy enough to go into the scanner data PIDs to verify the fault by looking at the coolant sensor reading. Keep in mind that in OBDII factory-enhanced mode some manufactures may mislead you by putting a substitute value in the data stream to run the vehicle in a failsafe mode, but that was not the case here. When viewing the coolant sensor PID you could see the -40 degree reading indicating a definite open coolant sensor circuit (Figure 3). Now it was time to go do some visual inspections that included poking and probing within the engine compartment. 

Figure 4

It was hard to believe that the shop was at fault because the problem was engine-compartment related and the vehicle was hit in the rear, but at this point the garage needed to get to the bottom of this dilemma and worry about who was going to pay later. While looking in the engine compartment everything seemed intact, but I had yet to dig deeper (Figure 4). As I removed the engine cover to gain access to the coolant sensor, I was taken aback by what I discovered. There were bits and pieces of blue plastic lying all over the top of the engine (Figure 5). 

Figure 5

The body shop worker that was near me starting laughing at my findings and told me that the blue plastic was material from the shop that was used to wrap their cars during paint prep. This was signs of a rodent at work and it was time for me to grab some gloves to protect my hands from the unknown. Keep in mind that rodents and rodent feces can be dangerous to human health, and I wasn’t going to be taken down by rodent intrusion. As I dug even deeper and removed the plastic particles, I discovered that this rodent had severed both wires of the coolant sensor and this was the cause of the hard start and check engine light (Figure 6). With the wires severed, the sensor wiring falsified a coolant temp reading of -40 degrees and created a hard start condition because the engine computer was over fueling the engine and fouling the spark plugs with excessive fuel. This problem was no longer the vehicle owner’s problem. It was now in the lap of the shop owner who has a rodent problem. 

Figure 6

What has always amazed me in this business is that you can never predict the outcome of a problem with a vehicle. There are so many variables that play a role, and I have seen many rodent issues in my career where mice or squirrels would climb into warm engine compartments during the cold months. They would even stockpile food or use whatever is available to build a nice nesting spot of choice. What I don’t understand is the chewing of wires. I’m am sure that by chewing on the wires it helps them to sharpen their teeth but what draws them to the wires in the first place is a mystery. There are many theories out there as to why mice do this and some include the fact that certain manufacturers have moved to soy-based wire coatings or manufacturers may use peanut oil as a releasing agent when the insulation gets applied to the copper stranding. The mouse is the only one that knows the definite answer for this one. 

Cars that sit for a long period of time for repairs or simply for storage purposes are prone to exposure to rodent intrusion. You have to make sure that you check your garage or a vehicle for food lying around that may draw them into your building or into the vehicle. You also need to be careful when storing the vehicles outside especially near wooded areas. It’s a good idea to possibly put moth balls, cedar wood or even peppermint oil in the vehicle to warn them off. The other method would be to keep some pet cats around and put them on payroll. I’m just hoping that this story has hit home with you and that the next time you encounter an unexplained problem you need to keep an open mind before you start pointing fingers in the wrong direction.  

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