Warning Lights and Fault (DTC) Codes

Discussion in 'Gen 2 Prius Main Forum' started by EEG, Aug 14, 2010.

  1. EEG

    EEG Junior Member

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    2008 Prius recently lost acceleration (would only creep along) and soon stopped. Warning lights - red triangle with !, red split car on mid, check engine - came on. About 10 minutes later the car started and allowed my daughter to creep the last 1/4 mile home. DTC's - P0A3F and P2196. Was recently gassed up, so checked gas cap, thinking it may have set the oxygen sensor code. It was loose, tightened it. Pulled the EFI fuse for a couple minutes to reset the codes (not sure it did). Put the smart key back in and warning lights came on again. May have to take to dealer, but would like to have some notion as to what's causing this. Possibly related -- a couple weeks ago the 12V battery got drained overnight. Pulled it and recharged and everything seemed to be running fine. Any ideas?
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P0A3F "Drive Motor A Position Sensor Circuit": this was logged by the hybrid vehicle ECU and shows a problem with the transaxle, hybrid vehicle ECU or the wiring harness.

    DTC P2196 "Oxygen Sensor Signal Stuck Rich": this was logged by the engine ECU and shows that the fuel/air mixture is rich. This is a problem with the air/fuel ratio sensor, injector, or engine ECU.

    The two DTC are unrelated, so this implies your car has two separate problems.

    - Vehicle odometer reading?

    - What are you using to retrieve the DTC?

    If you have any concern about the 12V battery's condition you may wish to replace that first. When the battery is disconnected for 5 minutes, then the DTC should clear unless the root cause remains.
     
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  3. EEG

    EEG Junior Member

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    Bought it used a couple months ago, current mileage slightly over 40,000. What about the loss of acceleration? Two other symptoms -- audible on ign on -- two quick beeps, four beeps pause single beep. Using Actron CP9125 to pull codes. Just used the code scanner to erase codes, turned power off then back on and codes were gone. Guess I'll try driving it a while to see if this happens again.
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, the loss of acceleration is troublesome. Maybe the transaxle or hybrid vehicle ECU really has a problem. It would be a good idea for you to drive the car (instead of your daughter) and see if the problem comes back.

    I do not recognize the significance of the audible beeps. Does your car have a nav system? Maybe there's some reminder in memory?

    With 40K miles, the car should be covered under the powertrain and hybrid system warranties, so if the codes come back I suggest that you visit your local Toyota dealer.
     
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  5. EEG

    EEG Junior Member

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    Thanks Patrick for your input. I've driven the car on a test drive with no apparent problems and no return of the warnings. Also noticed that once the DTC's were erased the audible beeps on power on are two quick beeps followed by three slow beeps. Think I'll look for what they mean. Thanks again. I'll post a follow-up to this thread if issues return in the near future.
     
  6. northwichita

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    Possibly related -- a couple weeks ago the 12V battery got drained overnight. Pulled it and recharged and everything seemed to be running fine. Any ideas?

    I recently dealt with an assortment of trouble codes, due to my not tightening the ground for the 12V battery securely with a wrench, the hand tightening I did during testing was a mistake on my part. So rechecking the batteries connectors would be a good idea if you haven't already done this.
     
  7. EEG

    EEG Junior Member

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    Well, the same warning lights are back (P0A3F and P2196). It snowed yesterday and on the way home my wife (it's really her car) says she saw the ABS light come on and a loud noise for a second (possibly drive wheels slipped on the icy road?). She was very low on gas (gas refill light was flashing), so she pulled into a service station and filled up - made sure to tighten the gas cap until it was clicking as I have told her to do. When she went to drive off, the panel lit up again: Brake light, Warning light, VSC light, check engine (which had already been on because I need to change the oil) and the dreaded triangle with the exclamation mark. Of course, the car would not start -- it would power up but never get to the ready state and you could only move the shift lever from park to neutral and back again. I was called to come help. When I got there I smelled a strong smell of gasoline (but it was still sitting at a gas pump after all). I checked the gas cap - tight, but I got the same result as above. Decided to push it to a parking space and come back to deal with it this morning. Today I took my code reader and when I got to the car it powered up but still had the MID lit up. I read the codes - P0A3F and P2196 again. I cleared the codes with the code reader and all seemed well. Drove it home with no problems. Might mention that I replaced two air sensors in front of the catalytic converter about a month ago, but don't think that had anything to do with this problem. The codes were clear before yesterday and it had been running fine. Any comments?
     
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Note that your OP as well as your most recent post indicates that these problems are happening as soon as the car is refueled.

    1. Since you apparently were able to drive the car without incident for a five-month period of time, I would say that the problem is not mechanical.

    2. As a workaround, I suggest that you ask your family members to refuel sooner, like when two or three bars remain on the fuel gauge.

    3. If #2 is not feasible, then the next time the car has a problem, I recommend that you take the car to your local dealer to have the DTC read and a diagnosis provided to you, as it seems possible that your code reader is not reading the correct codes.

    4. The air/fuel ratio sensor is upstream from the catalytic converter while the oxygen sensor is downstream from the catalytic converter. Did you replace those two parts with the intent of solving the DTC P2196 problem? Did you use the correct Toyota parts or aftermarket?

    Good luck.
     
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  9. EEG

    EEG Junior Member

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    3. If #2 is not feasible, then the next time the car has a problem, I recommend that you take the car to your local dealer to have the DTC read and a diagnosis provided to you, as it seems possible that your code reader is not reading the correct codes.

    4. The air/fuel ratio sensor is upstream from the catalytic converter while the oxygen sensor is downstream from the catalytic converter. Did you replace those two parts with the intent of solving the DTC P2196 problem? Did you use the correct Toyota parts or aftermarket?
    -----------------------------------
    I'll start with the P2196 first. I replaced the a/f ratio sensors (both banks) with aftermarket and am now not so concerned with those. As you said earlier, the two dtc's are unrelated.

    The P0A3F has me puzzled though. It has happened three times recently. I've had to wait a while each time, erase the codes, then the car starts and runs fine again until the next situation. All three times the drive wheels have slipped slightly. The first and last times were while my wife was driving on snow or ice. I'm told she was trying to slow down gradually and the wheels seemed to momentarily slip. The second time I was driving and ran the car through an automated car wash with a conveyor mechanism with the car in neutral. About two-thirds of the way through the car wash the warning indicators came on and once out of the car wash I shut the engine down. Of course it wouldn't start again for the next hour or so. I pulled the EFI fuse (#30) to hopefully reset the indicators and eventually the car magically started and everything seemed to be running fine again. Each time when you powered the car on and the warning lights lit I could not move the shifter into a forward or backward gear position. It would only go from P to N and back again.

    I think I must be getting the right code with my scanner, but suspect that there are subcodes which I cannot read. Tonight in freezing rain it took 4 hours to get my insurance company to provide a tow back to my house. So, it's off to a dealer for a better diagnosis with a request to check the Drive Motor "A" Position Sensor. I'll post the results.

    Thanks again for your input.
     
  10. seilerts

    seilerts Battery Curmudgeon

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    There is only one subcode for P0A3F, so no help there.

    The troubleshooting starts with the wiring harness between the HV ECU and MG2. Most likely your problem is there. Car wash, snow/ice, freezing rain -- there's something going on with that wiring harness most likely, insulation has been stripped and water gets in and causes a short? The only other two causes are the HV ECU or MG2. Either would cost you thousands for the dealer to replace, and that might be just what they suggest if they can't reproduce the problem.
     
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  11. EEG

    EEG Junior Member

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    Thanks for that info seilerts!

    I'll at least visually check the wiring harness before I take it to the dealer. We're iced in today, so that won't be for a little while.
     
  12. Sam Brinson

    Sam Brinson New Member

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    I wonder if he ever figured it out. I'm getting a P0A3F in my 2007 Prius.
     
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