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PCS malfunction light on b/c I forgot to plug in the MAF sensor?

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Dusttttt, Jan 9, 2023.

  1. Dusttttt

    Dusttttt Junior Member

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    So I checked the air filter today and then forgot to plug in the MAF sensor. I drove maybe 100 feet and then ALL the warning lights turned on. Pre-Collision System Malfunction is one of them. I plugged the MAF back in and was able to drive around the block and the car drove perfectly, but the PCS light is still on. I read similar threads about the PCS and some people said it was bad 12v battery, the manual says 100 reasons why this system malfunctioned but forgetting to plug the MAF sensor back in wasn't one of them. I'm positive that is the reason why it came on. How can I fix it? Thanks.
     
  2. jerrymildred

    jerrymildred Senior Member

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    You're kidding, right? What could the mass air flow sensor on your engine possibly have to do with the pre-collision system? Go back to your manual and see if you have any of those conditions that might actually cause it to fail.
     
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  3. Dusttttt

    Dusttttt Junior Member

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    Not kidding. That’s why I’m asking here because it can’t be coincidence that these 2 things happened at the same time. I went through the manual and in the 100 feet I drove, nothing obstructed the radar, no cars, pedestrians, etc so nothing applies to this. Thanks for the reply.
    No. Why do you think I would waste my time to create a post and only be kidding?? Yes, it doesn't make sense that these two issues be related to each other, so that's why I'm here asking for help. After going through the manual again I can confirm that I didn't set off the collision radar by-- any vehicles in front of me, no pedestrians, no obstructions on the side of the road, no low overhead clearance also the sensor is not dirty. I drove in a straight line for 100 feet and then the car wouldn't move and all the MIL lights came on. I instantly realized I forgot to plug in the MAF sensor. I plugged it back in and it drove perfectly for a 6 mile trip. The PCS light is still on and its telling go to the dealer.
    This car is 5 months new to me and I haven't had a single problem to date. It just so happens that an hour before I drove it, I disconnected the MAF sensor before I turned on the car and drove 100ft and all these lights turned on. So maybe it's a coincidence? I'm not sure but thank you for the reply.
     
  4. CooCooCaChoo

    CooCooCaChoo Active Member

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    Was there something else you were checking besides the air filter? The MAF sensor doesn't need to be disconnected in order to look at or replace the air filter. Maybe you forgot to reconnect something else?
     
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  5. jerrymildred

    jerrymildred Senior Member

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    Because the two systems are so totally unrelated.

    Leaving the MAF disconnected will for sure trigger some lights, but it won't affect the pre-collision system. I'm also curious if you disconnected something else. As @CooCooCaChoo said, there's no need to unplug the MAF to change the air filter. In fact, there's no need to disconnect anything, so I can't guess what you might have unplugged. If nothing is unplugged, then there is something broken and coincidences really do happen sometimes.
     
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  6. BiomedO1

    BiomedO1 Senior Member

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    Since the car is 'new to you'; what's the history? Has it been in a front end collision? You may have an intermittent after-market replacement part in there, tripping the sensors or a bad sensor. What is the current voltage reading at the battery and at the 'jump-point' under the hood?
     
  7. Dusttttt

    Dusttttt Junior Member

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    So last night I checked for trouble codes and P0102 & P0113 both were current faults.
    P0102 - Mass or Volume Air Flow Ciruit Low Input
    P0113 - Intake Air Temperature Circuit High Input

    I was searching about these (2) codes happening at the same time and several other people experienced it. It seems like everyone was doing maintenance on their car and after unplugging the MAF and then connecting it back these codes would show up. One solution was that it would just fix itself after x-number of drive cycles, Another person said compressed air fixed it. I do not know. I cleared the codes and turned back on all the PCS sensors so I'll see if that fixes it hopefully. Didn't know I could leave the MAF connected, I'll remember that for next time.
    But that still doesn't explain the PCS, maybe it is coincidence.
     
  8. jerrymildred

    jerrymildred Senior Member

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    That's pretty amazing that there could be any correlation between those sensors and PCS, but sometimes there's no explaining the reasoning of programmers. LOL! I've unplugged both those sensors probably a hundred times at work and never got a PSC fault on the few times I forgot to plug them back in.
     
  9. MalachyNG

    MalachyNG Active Member

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    Are those wire harnesses anywhere near each other? Could unplugging one jiggle the other loose?
     
  10. jerrymildred

    jerrymildred Senior Member

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    The MAF sensor is at the back of the top of the tube feeding air to the air filter box. What I assume is the intake temperature sensor is down by the drivers side of the throttle body. As for the PSC sensor cable, I don't know, but it's not close to the air filter box. If I remember right, that's routed in front of the radiator to where the sensor is.

    BTW, turning off the PSC system will also turn on the light. So it's not necessarily indicating a problem when it's lit.
     
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    This works. Everything may be rectified, but the car will continue to show trouble lights. It’ll take 4 or 5 start up, and the the lights shut off, not all at the same time.

    I had this happen after leaving an oil catch can hose disconnected.
     
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  12. mr_guy_mann

    mr_guy_mann Senior Member

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    So, on modern cars EVERYTHING is interconnected. Most of the Advanced Driver Assistance Systems (lane departure warning, collision avoidance, etc, etc) require that braking systems (duhh!) and powertrain (torque management) have no faults.

    Since these systems are doing "active" interventions to keep you alive, the engineers designed things to shut down if something can't be relied on to do what's expected .

    Posted via the PriusChat mobile app.
     
  13. CooCooCaChoo

    CooCooCaChoo Active Member

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    Case in point: The tail lights on the new NSX will prevent the car from starting if they are blown out

    Acura NSX Recalled to Fix Faulty Fuel Tanks and Brake Lights