2001 Prius - P3000/123 & P3125/287

Any time you are in ON especially if the engine is running, the 12V battery should be seeing 13.5 to 13.9V.

"287-Auxiliary Battery Voltage 11.52 V"

So figure out what relay or reason the 12V battery isn't being charged. The DC-DC or maybe some other condition. Maybe clear codes and see if it happens again or if this is all related to ICE stalling.

 

This is what attracted my attention:

The temperature relationship should be:

MG2 < MG1 < ICE temp

The first code event showed MG2 well in excess of boiling temperature, 273F. This is dangerously high and even though it looks like outside temperatures were scorching, this is way too high.

The second one shows evidence the 12V DC-to-DC convert is bad. This is bad news. It also shows MG2 temperature too high relative to MG1.

Do you hear a low rumble that increases in pitch with speed? Does the rumble remain if you switch into "N"?

These are the symptoms of failed, MG2 stator, and this is not a trivial problem to fix.

Bob Wilson

 

Why didn't the engineers put in a cut off red triangle for MG2 / MG1 over a certain temp?

From the burnt out winding pics and readings of others, it appears the software only checks for inverter overheating, and will gladly let the motors burn up. You would think the software could just shut down until the motors cool off or at least put up a little warning light for various inv coolant too hot, regular coolant too hot, motor/ATF too hot. Did they implement it for Gen 2?


If I'm reading it correctly, the first code was thrown and the inverter warning maybe because of a self-protect condition... (Not a stall)

Engine RPM 1184 rpm
Vehicle Speed 22 MPH
123-Generator(MG1) Rev 768 rpm
123-Motor(MG2) Revolution 1280 rpm
123-Request Power 9120 W
123-Power Resource VM 304 V
123-Power Resource IB 0 A

So that appears to me that based on the gas pedal, the car was requesting to accelerate and all the motors were spinning but IB of 0A means that the HV battery wasn't sending current to MG1/MG2 which were requesting 9kW.


-------

The second code was thrown because it was trying to idle and charge up the HV battery, but the ICE stalled or wasn't running. MG1 was matching MG2 (?). I'm not sure what mode this was because the fuel was cut but it was supposed to idle and there is no charge request and the HV battery was sending 16A to MG1/MG2 to spin each other. But somehow the DC-DC wasn't charging the battery. Could this be a code when MG1 is acting as a starter motor for the ICE?

Engine RPM 0 rpm
Vehicle Speed 1 MPH
287-Generator(MG1) Rev 1152 rpm
287-Motor(MG2) Revolution -128 rpm
287-Request Power 0 W
287-Power Resource VM 292 V
287-Power Resource IB 16 A
287-Engine Stop Request No
287-Engine Idling Request Yes
287-Engine Fuel Cut Yes
287-Main Battery Charg Req No
287-Engine Warming Up Req Yes
287-Auxiliary Battery Voltage 11.52 V

 

I'm pretty sure the manifold has a water jacket but I agree the intake air temperature sure looks 'funny.' I'll check my shop manual this weekend.

Holes in the intake box?? . . . Not standard and would explain the higher temperatures. It makes sense to replace the box.

On the MG2 stator, a short trip around the block can confirm the diagnosis. If MG2 temp exceeds 100C (212F), you'll want to get back to the parking place. If MG2 is burned, you'll see MG2 temperature climb very rapidly as well as the 'rumble.' IF you have time, I need an audio recording that includes calling out the indicated MPH (or MG2 rpm) and the audio rumble while the car is rolling in "N." If you can get it at say 25 mph that would be prefect.

The reason is we've had others with failed transaxle MG2 stators and the symptom has always been called a 'rumble.' If we could get an audio recording at a constant speed, say 25 MPH, the frequency as well as the audio recording could be used in the future to help the next person with a failing MG2 'get a clue.'

I understand Lucious Garage developed an MG2 stator replacement procedure. However, I lean towards a used part replacement. IMHO, transmission rebuild work should be done on a bench. But you know your capabilities and can make the best choice . . .

Thanks for sharing,
Bob Wilson

​

​

 

For what it is worth, I don't think IAT 10degF or more above ambient in unusual. You have quite a bit of heat trapped under the hood and especially if the engine is hot and parked in the sun on the hood, the ambient air coming in is heated by all the hotter plastic and metal the air passes by. Especially if you are driving under 30 mph. I've always seen pretty warm IAT especially when it is over 80degF outside.

 

With an infrared thermometer driving in 95degF air temp for 15 mins, almost everything in the engine was 115degF. All the PVC air intake and box was 115degF, the engine block was over 140degF and the throttle body metal housing with the MAF (and IAT?) was 145 degF.

I believe the short intake in the cramped engine bay means the intake air gets warmed quite a bit at low speeds. I just cleaned the MAF resistors and the bigger thermocouple I assume is the IAT sensor, so there isn't any buildup on it.

133 seems high, maybe I check it after letting a hot engine sit in the sun, but I imagine if the ICE was not running, there is no air moving past the sensor, so doesn't seem unreasonable to me.