Tuesday, March 6, 2012

2004 Jaguar S-type won't upshift

So today I got a S-type with the code: 
  • P1646: HO2 sensor sensing circuit.
Bad O2 sensor was the most likely cause but for a while I didn't pay no mind to it because the check engine light wasn't the customers main concern. The main concern was that the transmission wouldn't up shift until he let go of the gas. In other words, you would accelerate and it will stay on first gear, and then after you would let go, it would jolt you forward by up-shifting. I wanted to check everything I could before selling the customer an O2 sensor and after he spent his money realize that that wasn't the cause and tell him: "Oh BTW, you need a transmission..."

With the Jag IDS, I pulled transmission codes but there weren't any. I look at everything I could've possibly looked at, so I finally told the customer to let me fix the O2 and see what happened. It did fix the problem. I'm just very surprised that the transmission wouldn't shift. I figured that the car would shift wrong and rough, not this symptom. Anyways, the conclusion is that before diagnosing anything else make sure you have a well running engine with no codes.

S-type O2 sensor to be replaced
If you are replacing the Oxygen sensor I recommend the following link: Denso 234-9030 Oxygen Sensor

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