The Sad Saga of the 2007 Lexus ES350 and a P0051 AF Sensor Heater Circuit Code

by | Dec, 2021 | Electrical, feature, Toyota, TOYOTAtech Features | 4 comments

Some months ago, I was called to a shop to assist in the diagnosis of a 2007 Lexus ES350 (Figure 1) with a code P0051, “A/F Sensor Heater Control Circuit Low (B2S1)” (Figure 2). We’ll call this shop “Shop B.” Another shop, let’s call them “Shop A,” ...

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  1. Johnny Nguyen

    Thank you so much for your post, i fixed my coworker 2007 lexus es350 same exact problem, the ground juction B32 plug was lose from ground cap, someone reinstall the engine and did not plug all the way down, Pin 46 white wire grounded to the juction B32 plug.

  2. Newfiemech

    So did you find the fault with the existing ground and repair it or just splice in a new ground? No judgement , I’ve done both depending on the situation, just curious. 😊

    • Automotive Tech Info

      Hi Ted,
      This came from the writer:

      I looked for the problem with the ground wire. The location for the ground was found and there were multiple grounds connected at the same spot. There was evidence of rodents having been under the hood and when that is the case, I like to find where the wires have been chewed. However, this one had no sign of chewed wires that I could find; only the smell of rodent urine and a few feces. I cut the wire just outside of the PCM and grounded it; not my preferred method of repair as I always fear that an additional failure will show up down the line due to the original source of the problem not being found and corrected. Sometimes you have to fish or cut bait and this was the decision I made.

  3. Pete Moler

    Edwin, Loved the fact that you found the answer to your problem, lots of perseverance! I had a similar issue with a neighbor’s 2004 Chrysler Sebring. It was a P0134 for B1S1 heater circuit. This heater is constantly grounded, the positive side is duty cycled through the ECU. I got to look at the vehicle after the second O2 sensor and first engine ECU. I scanned the circuits involved and everything appeared to be okay when I was looking at it. Finally I got it to act up, the ground to that sensor was intermittent. Repairing the faulty ground wire finally fixed the problem.

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