Reduce engine power

Hi,

When you say EVAP pressure sensor, I assume you mean the fuel tank pressure sensor. If you look at the first chart in the attachments, you will see this DTC is set if there is high resistance in the 5 volt reference circuit, or the signal circuit. Also, it is set if there is a signal performance issue which would be the sensor. My guess is, this sensor was fine but there is a connection issue and by the tech removing the connector and putting back on the new sensor, he re-seated it and it worked okay for a while. Again, this is just a guess based on the info provided. I would suggest scanning codes again and confirm you have the same one and then testing the circuitry.

The other possibility is replacing the sensor did not fix it and the tech was able to clear the code. Then it took a little while to reset. The actual cause could be a restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set.

Let me know what you find after you review these documents and we can go from there. Thanks

I think it is related. It may not be turning the check engine light on yet because it is what is called a multiple trip failure. This means it needs to see the same fault happen on subsequent key cycles before it turns the light on. However, the code might be there but when you disconnect the battery it clears the fault, then you drive it, it sees the fault and derates the engine. The code most likely goes pending (no check engine light) then when it sees it happen again, it will turn the light on and the code will go active. Either way, we need to monitor the system which driving to see what it is doing. Unfortunately, this is an issue that we need a scan tool in order to see what the module sees from the sensors.

Sorry for the delay. I was waiting on a response from a contact I have in the Houston region. I am in Virginia so I didn't know of any in that area. However, they recommended any of the Christian Brothers Automotive facilities in the Houston area. While I don't know these individual stores, I am familiar with this organization and in general they are very highly regarded.

Without knowing the exact issue, it is hard to say. It also depends on the facilities door rate but if it is a wiring issue as I suspect, it shouldn't be more than a couple hundred dollars. However, to diagnose it they should charge you a flat rate (normally one hour based on their door rate). So if their door rate is $100.00 per hour, they should charge you $100.00 and then tell you exactly what is wrong with a price to do that work. If they can't figure it out, then the proper business practice is to not charge you because they didn't diagnose it.

I am well aware that not all business' do this and they charge the customer no matter what but I personally never agreed with that. You are paying for a service which is for them to diagnosis it. If they do not diagnose it then they did not provide that service. They attempted to provide a service, but I wouldn't pay someone to come clean my house then they get here and say, "sorry I can't do it" and pay them anyway.