[EXPLAINED] WNA5 & DRIVE SYSTEM CONTROL FAULT

[ct14garage]

Another common Taycan problem, you floor the car (or a significant amount of throttle) and suddenly the car gives out with either of the warning messages above and you've gotta crawl to a stop. Restart the car, everything is fine (until you floor it again that is).

If you get this sysmptom very sporadically, then you need not worry. But if you get this almost everytime you floor the car, go on.

The failure is caused by no less than the part which Ive covered with a square. This is called POWER ELECTRONICS, MOTOR CONTROL UNIT, or informally INVERTER. This electronic unit converts the DC electricity from the battery into 3 phase AC power which the motors need, this unit is also responsible of feeding each of the 3 phases of the motor with the appropriate amount of current according to driver's throttle inputs.

Any AWD Taycan has two of these inverters. One at the front one at the rear

When this failure occurs almost everytime you floor the car you will see the following fault code:

P0E9D00 - Current sensor short circuit to ground. The moment you see this fault the inverter is DONE. Porsche techs will reprogramm it but it will make absolutely no difference.

The only solution is to replace the unit


This unit is made by HITACHI in Japan and what goes wrong is the current sensor (and its circuitry) at the AC output. Which works esentially just like any of those clamp current meters you have at home.

This is the current sensor. As you can see it sits on top of each of the 3 AC output phases and measures the current going through them. The part in question is HAH3DR current sensor

I have ordered this exact sensor and replaced it in failed inverters, but haven't been able to successfully repair the unit. After replacing the sensor the issue persists which indicated that there's also damage to the circuitry that drives and controls the sensor but I am yet researching a way to fix this.

This is a relatively common issue in Taycans, although far less common than the battery issues.


If you are lucky and the failed one is the front inverter, replacing it is quite simple.

But replacing the rear inverter implies dropping the battery and the entire whole axle which is quite a lot of work!!

As you can see a lot of hours of work.


PS: The reason why Porsche dealer techs will try to recalibrate and reprogramm the inverter is because there is another campaign for cars with the same symptom which is indeed caused by a software bug and solved by a reprogramming...... However the fault codes aren't the same. What I am reporting above is a different issue and Porsche is well aware of it:

Keep in mind that this is different to what I reported above. This is for fault code P061B00 accompanied ALWAYS by 00AC80.

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[r553]

After getting Red Engine Control Error and the car stalling I was able to restart the car and drive to the dealer. They could not duplicate the fault but found U178800 "Front Power Electronics-Drive Fault" and P061B00 internal control module torque calculation performance. They say my car will likely need front power electronics but needs to fail again before proceeding with replacement.

 

[ct14garage]

No it doesn't need yo happen again lol

Front PE is fucked lol.

Floor the car if you can using launch control it will happen again

 

[udubfl]

Couple months ago, I had similar situation where my wife was driving into our neighborhood in slow speed and the car died and she had to restart. So, it doesn't have to be in hard gas peddle situation. I was assuming it was the inverter and couldn't comment until now.

Only happened once but didn't want to risk anything while my family was driving it. So, took it into Porsche for check-up. They found an error code and cleared it and went for a drive. Fortunately, the error message/dead car thing happened while the tech drove it. Came back and he got the P0E9D00. I say fortunately because it only happened once for couple months and not sure how easy its to replicate the situation easily.

They had to replace the rear inverter. And as some of you have indicated, it's about $10K job. Not covered under battery warranty. I have Fidelity and they needed extra paperwork, etc. from Porsche to approve. As of Nov 2025, Porsche SA said the new inverters was in the stateside so not much to wait for parts. Porsche kept it couple days after installing the new inverter to tests for couple days. All seems good. Picking it up tomorrow.

As always, appreciate this forum.

 

[Caraholic]

Thanks for the write up had this happened to both of my taycans. Just another reason to never own this out of warranty. Wish we had an independent like CT4 here in the states.

 

[udubfl]

Well, it’s only been few months and I got another red Engine Error message. Figured it was the front one since I had the rear one replaced. Took it in yesterday and below are the fault codes my SA sent me…

P061B00 - Front high voltage electronics - Internal control module torque calculation, Performance
U178800 - Front axle power electronics control uinit - drive fault

They reprogrammed the front one as ct14garage said they would do. They test drove it for 60 miles for couple days and no issue.

We shall see if this fixes it or if another code comes up. To replace and be covered by warranty, SA said they need to replicate the code. Only happened once at 18mph speed and wasn’t punching the accelerator.

 

[mcs618]

@ct14garage

I got P0E9D00 - Current Low when checking my car with MapEV

Not “short circuit to ground”. Is this the same issue

 

[ct14garage]

@ct14garage

I got P0E9D00 - Current Low when checking my car with MapEV

Not “short circuit to ground”. Is this the same issue

Same. The description in MapEV is wrong. Fault code is same

 

[mcs618]

Same. The description in MapEV is wrong. Fault code is same

yeah I figured since it was the same code. It has only happened to me once so far but I assume it will happen more and more often?

 

[prj]

@ct14garage

I got P0E9D00 - Current Low when checking my car with MapEV

Not “short circuit to ground”. Is this the same issue

Short to Ground and Low are identical and which one is displayed depends on the PIWIS database used. IIRC it was different for UK and US.

Same. The description in MapEV is wrong. Fault code is same

Not wrong, it's interchangeable. MapEV Diag uses Diag-RA descriptions for the status parts (internal VAG development tool).

 

[ct14garage]

Not wrong, it's interchangeable. MapEV Diag uses Diag-RA descriptions for the status parts (internal VAG development tool).

Yes, just not the PIWIS description anyway

 

[prj]

Yes, just not the PIWIS description anyway

I think if you swap PIWIS language between English - UK and English - US the descriptions will change
Could also be that PIWIS is the same and it was like that in ODIS. But in one of the two 100%.

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