Sudden Warning Lights

DTC P0101 shows a problem with the mass air flow sensor.
DTC P0171 shows that the air/fuel mixture is too lean.

I suggest that you start by cleaning the MAF sensor. There are a number of posts that explain how to do this. Use only MAF sensor cleaner which you can buy at your local discount auto parts store, and remove the sensor so that you can spray the cleaner at the two wires within.

I also suggest that you inspect the engine air filter by holding it up to sunlight, and replace the filter if you cannot see light coming through the filter. Compare to a new filter if you have any doubt. This will probably cost ~$20 or so at your local dealer's parts dept.

 

Have you checked your oil level to make sure the quickie oil change place didn't over fill?

 

Well, let's first determine what's wrong with your car. Then we can hypothesize about whether the oil change place did anything to encourage that failure.

An excellent idea.

 

Yeah, the quick lube probably caused the problem. They were no doubt in the vicinity of the intake to check the air filter and see if it needed to be replaced. Other than the oil level, check under the hood for anything obvious -- disconnected/broken wires, etc.

 

It's possible that with a large enough overfill the oil will froth and more oil will get sucked through the PCV valve which could cause those problems.

Checking warm or cold wont make all that much difference. Do make sure it is parked on a reasonably level surface and that the car has been off at least 5 to 10 minutes, otherwise oil will still be draining back to the sump.and you'll under-read.

I think you should always check your oil level after getting it changed anywhere, especially at a quick lube type place.

 

An overfill of 1/2 inch it too high, you should drain some oil until the level is correct. Get it on the upper dot or even just a little below (1/4" under is ok).

BTW. The oil would still have been very cold when you tested so the oil would still be draining back after 10 min. So the actual overfill is probably a little worse than what you measured. You didn't need to drive around the block, it would have been more accurate to just pull the dipstick cold and take a reading.

 

I agree, definitely overfilled! If the place is close by, I would go back and raise holy hell and get them to do it right. Overfill can cause all kinds of problems, including blowing out seals which will cause leaks!

Strangely, I'm not sure how those codes relate, unless they only got the generic codes (possible) and missed the Prius-specific ones because they have a basic scantool.

 

1/2" overfill sounds like you might have 4.5 quarts or more in the crankcase. I suggest you drain 0.5 quart and then recheck the level.

Then, clean the MAF sensor, disconnect the 12V battery for a few minutes, reconnect, and see if the car still has warning lights.

 

In the future always check the oil level yourself before driving away from every oil change, no matter who does it. This can prevent annoyances and expensive damage.

 

Hello All,


After buying a used 2005 with 15K Prius in Nov. 2007, I have been very happy with it.

Back in Nov. of 2009 I was driving along and all of the sudden the ((!)), ABS & Red BRAKE indicator lights came on. I promptly pulled off the road and read the owners manual which seemed to indicate that I should take the car to my Toyota Dealer.

Since the closest Toyota Dealer is about 25 miles away and this problem occurred on a Sunday (the Toyota dealer is closed) I did a number of "braking" tests on the side of the road. The braking tests seemed to indicate that there was not any real problem with the braking system so I cautiously drove the car home (about 30 miles).

After getting home and turning the car OFF I needed to take the car for a quick errand so I started the car up and the lights went ON (as all of the indicators do when the car is turned on) and then went OFF. The car drove just fine and I turned it OFF when I got to the market. I turned the car back ON when I was done shopping and drove the car back home without any indicator lights coming ON. I thought that the issue may be a nuisance error so I thought that I would drive the car while keeping an eye on it.

During the next couple of weeks the indicator lights would come on sporadically in the same way as mentioned above. Usually, they would come on at some time when I applied the brakes, but it would also come on just while driving without applying the brakes.

During that time I looked around on the web to see what the Prius community knew about this. There is a lot more information on this type of issue now than when I was looking into it in 2009. Back in 2009, from what I could find, the problem seemed to be probably caused by an intermittently loose connection on one of the Wheel Speed Sensors.

After the couple of weeks of having the issue pop up intermittently, the problem went away until yesterday. Yesterday it came back and seemed to happen every time that I drove the car. Sometimes the lights would come on the first time I pressed the brakes and other times it would come on after driving for a few minutes. Then yesterday evening I stopped the car and went away for about 15 minutes.

When I came back to the car I noticed that the car was making a strange noise that I had never heard before. I am quite familiar with the typical noises that the Prius makes like the Engine Coolant Pump and the Brake Pump. This sounded different. I popped the hood and tried to locate the sound but I could not really pinpoint it. As far as I could tell it was somewhere near the drivers side on the engine side of the firewall in some of the components that are in that area.

Because something was definitely running I thought that it would eventually run down the battery, I opened the fuse/relay box on the driver's side. Thinking that the problem probably was something to do with the ABS, I first pulled the ABS No. 2 relay. The noise did not stop so I pulled the ABS MTR 2 relay as well but the noise did not stop. Then I pulled the ABS MTR relay and the noise turned off....Hooray!

I looked at the relay and it looked like it may have some heat damage near one of the high current terminals (see photo). I left the relay out and started the car up and drove down a long driveway. The brakes seemed to work okay but the indicator lights where ON all of the time. I drove a little on a seldom traveled rural road and the car seemed to drive well, but as I remember reading somewhere the re-gen would not work. By the way I live on the central coast of CA that does not have bad weather (no snow or ice) and I also live in a rural area so I do not drive in a lot of traffic.

Last night I did a crash course on the web on what I could find out about why the indicator lights came on. I was impressed with all of the good information that the community has been able to put together. After looking at many, many posts I think that I have come up with a strategy to try to diagnose the problem.

First, according to the community, I needed to check the AUX Battery. The AUX Battery was replaced with a new Factory Toyota battery soon after I bought the car back in 2007. I hooked up my Fluke Digital Multimeter to the positive terminal in the Fuse/Relay Box.

I hooked it up about 45 minutes after driving the car for about 7 miles / 9 minutes with the car OFF. The voltage was 12.75V. I turned the lights on for about 45 seconds. While the lights were ON, the voltage went down to 12.12V but when I turned the lights OFF it quickly went back to 12.71V. Please note that these readings were made with the ABS MTR relay removed.

I bench checked the relay and the resistance across the control circuit terminals was 18 ohms which sounds about right. With the control circuit NOT energized, the resistance across the high current terminals was > 20 Mega ohms. With the control circuit energized with 12 volts, the resistance across the high current terminals was 0.2 Ohms which sounds about right.

Then I turned the car ON to the READY state and without the engine running the voltage was 14.1V. While the car was in the READY state I opened the Inverter coolant reservoir cap and while I did not see a lot of turbulence, I could definitely see some small ripples in the surface of the coolant. I also located the Inverter coolant pump and put my hand on it. It was definitely running and it seemed to be running quite smoothly and not making any noise. Since my car is a member of the recalled cars for replacing the Inverter coolant pump I do expect to take the car in to have it replaced in the near future.

While the car remained in the READY state, I turned the headlights on again and the voltage dropped a little to 14.0 volts but seemed to be very steady. I think that these readings indicate that the AUX Battery, the Inverter and the Inverter coolant system is functioning within limits.

Now I turned to trying to do some of the diagnostic steps outlined by the community.

With the car OFF. I installed the "diagnostic" paperclip between the 4 and 13 terminals of the ODBII connector. Then I turned the car ON and into the READY State. The ((!)) light was flashing codes 36, 53 & 57. The ABS light was flashing codes 32 & 42. The Airbag was flashing code 14. Please note that up these checks were done with the ABS MTR relay removed from the Fuse/Relay box.

Then I turned the car OFF and reinstalled the ABS MTR relay into it's connector in the Fuse/Relay box. With the diagnostic clip still installed, I turned the car ON and into the READY State. With the relay installed, the code for the ((!)) light was only 53, the ABS flashed only 42 and the Airbag flashed 14 as it did before.

Because the ABS MTR relay has an indication that it had been heat damaged on the one high current terminal I am going to get a new one in the next few days. I am also going to try to keep an eye (ear also?) out to see if the relay causes the noise to come back.

Does anyone know what the diagnostic codes that I got mean?

Sorry for the long post but I really did learn a lot by reading all of the wonderful posts and thought that it would be best to present all of this information in one post so that it could be properly interpreted by the community.

Thanks!!!

PriusCruzer

 

Congratulations to you for performing a very comprehensive set of tests.

The 53 code coming from the ((!)) light indicates a problem with the ABS MTR relay, ABS MTR2 relay, the associated wiring harness or the brake actuator assembly.

The 42 code from the ABS light indicates a problem with 12V power to the skid control ECU, perhaps this was induced when the relay was previously removed.

The 14 code from the air bag light indicates a problem with the LH airbag deceleration sensor. Had the car been in a front-end accident impacting the LH side of the bumper? Do the air bag warning lights come on during normal driving?

Both the ABS MTR and ABS MTR2 relays provide power to the brake actuator motor. One of those apparently had stuck closed, which caused the brake actuator motor to run when it should not have.

I agree with your decision to replace the ABS MTR relay. Perhaps it had stuck in the closed position while the car was IG-OFF. In addition, I would suggest that you also replace the ABS MTR2 relay while you are at it. Relays are relatively inexpensive, and those two relays provide backup for each other.

Then, after replacing both relays, if you still have a problem then the brake actuator assembly may need to be replaced. Good luck.

For fun, pls check the coil terminal resistance of the new relay and compare to your 18 ohm measurement from the old relay. 18 ohms seems very low to me, this implies 0.7A current flowing to power the coil. I've measured the coil resistance of other relays, which is more like 100 ohms.

 

You can disconnect the 12v battery negative lead for a minute to clear the codes.

 

Ask the lube shop to reset it with their scanner. Disconnecting the 12V battery is a bit of a hack, and is useful only if you have no other choice and don't mind resetting your radio stations, navigation, etc. afterwards.

It's not, especially with that kind of weather.