DTC P1A29 Motor over current

[Harw40]

Hello

Recently I had the yellow light , ! Over the car , come on . No power to my throttle. Turned key off then on, light went out. Drove to town and back ( 40 km) all ok. Charged car up on level one completely until it shut off. Drove 35 km where I had the light come on, and subsequent loss of power, once more. Turned off, then back on, light out, on my way. Destination charged almost back to full and proceeded to have the light come on four more times on my way home. Basically whenever any kind of acceleration was called for, let’s say beyond 2 o’ clock it’d kick out. Also of note was the turtle symbol flashed a couple of times in all this, again with a heavy acceleration. I should say here that I’ve recently changed out my 12V , when I had the infamous charger issue six months ago.
I don’t have any battery monitoring gadgets so had it towed to the dealership to have a diagnostic test done. Their four page report was all on the DTC code they apparently got, P1A29. Motor over current ( EMCU) with the flow chart from the service manual. Page one, circuit diagram of inverter - ECU. Page two, showing check list of three bullet points, point one ;H/V connectors, G07, G08, G09. Point two, malfunction of the EMCU, point three, malfunction of the motor ( EMU). Well they cleaned the three connectors, (although I had no additional charge over my $120 diagnostic fee ) where they said they found corrosion, but same code came back up. So next is the EMCU. Cost installed $10,000 CAN. Actually a little over but hey, we’re friends here. Needless to say, my liquor cabinet has been taking a beating!
I presumed the diagnostic would have included a look at the battery seeing as it’s a high voltage issue but apparently not. So in desperation I’ve asked them to hook it up again to see if any cells show up weak. Thought I may be able to point the finger there as the problem. Or that the battery is suspect as well as , or because of , the failed EMCU. Or visa versa.
I’ve read through many of the posts here where low cells have shown to be the cause of failure and subsequent warranty. So in preparation for the ensuing report can anyone tell me what constitutes a failed cell? How much lower voltage than the rest? Is there a particular test I should be asking for? Thanking everyone in advance. This forum has already got me through the charger issue with its wealth of information.
Mark

 

[kiev]

Howdy Mark,

i had this happen years ago before i had the scantools available to read DTCs. And before i understood how critical a good strong 12V aux battery was for proper operation without nuisance issues and problems.

Do you have a voltmeter? If so measure the open circuit voltage of the aux with everything OFF, then get a helper so you can watch the voltage drop as they turn the key to ON, then as they turn the key to start, and then as the car goes to READY. So you are going to read 4 different voltages:
OFF
ON
START
READY

That might provide some clues about your issue. If you have a external 12V battery charger or automatic 14.4 charger with float maintainer (e.g. Yuasa 1Amp), then you might go ahead and attach it just to desulfate the aux and get it fully charged. If a lead acid battery is stored in a low state then permanent damage due to sulfation can occur in as little as 3 days.

There are 2 current sensors inside the MCU to read the motor phase currents, and these are powered up by a low-voltage supply that is derived from the 12V aux.

Has this occurred recently with the onset of a snap of cold weather in your area? Cold temperature is a big load factor on batteries also. There are 2 mievs in my local area that are having issues of the Turtle showing during acceleration after we had a cold snap come thru.

 

[Harw40]

Kiev, thanks for the response. Having just purchased the 12V aux six month ago it didn’t occur to me to think of it, especially as my condition seemed to be a H/V issue . So when you had this happen would it cause a complete shutdown of the H/V system or were you just getting the yellow light on? I do have a voltmeter and will do the checks you suggest when I get the car back home from the dealer this coming weekend.
I’ve asked them to do another diagnostic test, this time on my battery cell’s tomorrow .
I’m not too optimistic though as thus far the car is still charging to 16 bars , though they’re dropping noticeably faster now that I’ve been having this issue. Reading through the threads it seems like most warranty claims have been for those batteries that no longer fully charge.
Is it conceivable that a bad cell could cause a power down situation yet not affect the ability to fully charge?
Mark

 

[kiev]

Howdy Mark,

In my case it would cause complete shutdown and throw the HV error light (car with !). Replacing the aux got it working again. The car was later under a recall of the MCU; i was getting the P1A15 failure for the HV capacitor to reach voltage within time limit.

i'm working on a car right now that charges to 16 bars, but only gets about 30 miles before going to turtle. i put the obii scan tool and drove it from full to empty, and found that all the cells were withing 5 mV when full, but that cell #27 was about 0.6 Volts below all the rest as the fuel gage was reaching the bottom toward empty.

Also as the pack was getting lower, it would also go to turtle mode under WOT acceleration and the voltage dropped to 2.8 for that cell. No HV error and no shutdown, but that bad cell is causing a huge capacity and range reduction. i'm hoping it will just go ahead and fail such that the pack can be replaced under the 10 yr warranty for defective cells.

How's your aux looking?