inverter rebuild / troubleshooting - Voltage insulation fault P0AA6 526/614

When you're working through a troubleshooting sequence in the manual, it is very important to read carefully enough so that you know what each step of troubleshooting is supposed to be telling you, and which results are considered "OK" or "NG" (no good), and what the context is.

In the case of step 17 in what you posted, the context is that by the time you reach step 17, you are already convinced that either the inverter or the transaxle has a ground fault, and step 17 is there for you to decide between those two possibilities. (As to why you are convinced either one of them does have a problem, that had to come from the careful reading of the sixteen earlier steps).

Once you are at step 17, you are trying to decide whether the ground fault you think you have is in the transaxle or not. So it has you meg each of the transaxle motor leads to ground. For each of those tests, the "specified condition" is "10 MΩ or higher". So 10 MΩ, or any reading higher than 10 MΩ, is OK. A reading would have to be lower than 10 MΩ to be NG.

So if you have just made all six of those tests and they all showed "over 150 Mega Ohms" on your meter, well, "over 150 Mega Ohms" is way higher than 10 MΩ, so these tests are all way super-duper flying-colors OK, and there is definitely no ground fault in your transaxle.

Notice that these results do not prove that you do have a ground fault in the inverter. Rather, if you got to step 17, you presumably believe there is a ground fault in the inverter or the transaxle, and the step 17 tests have told you it's not in the transaxle, so if you are right about a fault in one or the other, then you could conclude the fault is in the inverter.

But at this point, it would probably not hurt to run back over the 16 earlier steps just to make sure, as in this example, of what each step was supposed to be telling you, and what each one did tell you.

 

That’s a very old edition of the Repair Manual, and you may wish to use one that is more up-to-date and that matches the model year of your car; see the PriusChat Wiki page for where to find them. There have been changes; for example, the procedure for P0AA6, at least for some model years, now warns against using megohmmeter settings greater than 500 volts, to avoid damaging certain parts.

Parts catalog Figure 84-31, HV Inverter, shows the internal parts of the inverter with converter assembly that are available from Toyota, including the power module intelligent transistor kit and the electric vehicle converter assembly. (Don’t read too much into the “Product Not Available” label for the top-level assembly; that may just be a data problem with the website.)

 

most people just buy a salvage inverter for cheap money

 

Hmm, you posted the page with step 17 but not step 18. I'm trying to follow along at home with only a 2006 manual. It does have a step 17 and a step 18, but in this version it doesn't look like you would ever arrive at both steps.

Rather, at step 2, you would be sent to step 18 only if you had INF code 613. If you had only INF code 526, you would be sent to step 3, step 4 could send you to step 15, and from there you could end up at step 17 depending on how the SMR and frame wire tests panned out.

But in your title, you've mentioned INF code 614, which would have sent you from step 2 straight to step 19, no? Steps 17 and 18 would have been barking up the wrong tree.

So, there's a chance it would be easier for us to follow along if you showed more of the work with the earlier steps, what your measurements were, and which steps they led you to.

Edit:

Just re-read this part of your earlier post. It's actually not surprising that the steps for INF 614 don't mention transaxle fault anywhere; that's the INF codes doing their job to help you out.

When the ECU first notices there's a ground fault somewhere, it sets only the 526 code. It uses that as a "note to self" to pay extra attention on the next drive cycle, and see if it can pin down the fault further to the air conditioning circuit (611), battery area (612), transaxle area (613), or high-voltage DC area (614). If it successfully does that and gives you a code 614, that lets the A/C and transaxle off the hook, and lets you really just focus on DC components from the inverter back to the battery, as steps 19 through 29 have you do.

 

Yes. The latest revision is available by subscription to techinfo.toyota.com.

No, I don’t. Keep in mind that Toyota specifies the internal parts directly in diagnostic procedures, when replacing them would be sufficient to correct a problem. For example, instead of “Replace Inverter with Converter Assembly,” the procedure would say “Replace Electric Vehicle Converter Assembly” or “Replace Power Module Intelligent Transistor Set.”

I also wouldn’t yet assume that there is a problem in the inverter with converter assembly. As @ChapmanF kindly points out, steps 3–18 in the P0AA6 procedure (in the old Repair Manual you’re using; the steps have been renumbered in newer editions) were written with the assumption that INF code 611, 612, or 613 has been stored, which isn’t true if you’ve only seen INF codes 526 and 614.

In the diagram on page HV-425, the dashed lines show possible the fault areas for each INF code. Code 614 indicates a problem in the inverter with converter assembly, the frame wire, the system main relays, or the system main resistor, which is why step 2 (pages HV-426–427) has you skip to step 19 (page HV-435). In step 19, by disconnecting the frame wire at the inverter with converter assembly, the first megohmmeter test can check for faults in the frame wire, system main relays, and system main resistor, all at once.

If the step 19 test passes, the fault is likely to be in the only part of the fault area that remains, the inverter with converter assembly. Notice that you don’t do a megohmmeter test of the inverter with converter assembly directly, presumably because the reading wouldn’t be meaningful or the test would damage it.

If the step 19 test fails, then in step 20 (page HV-436), you disconnect the frame wire at the other end (at the system main relays), so the second megohmmeter test can check the frame wire on its own. If the step 20 test fails, you’ve proved that—whatever else might be wrong—the frame wire has a fault and must be replaced. If the step 20 test passes, then the frame wire is probably OK, and the remaining steps have you test the system main relays and system main resistor.

After any repair, you’d follow this note under “Inspection Procedure” in the current Repair Manual, to confirm that the problem is gone:

• After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output. (Do not turn the power switch off during this inspection.)

a. Apply the parking brake and secure the wheels using chocks.
b. When the vehicle is stationary, turn the power switch on (READY) with park (P) selected and wait for 75 seconds or more.
c. Turn the air conditioning system on (MAX COLD, blower speed HI).
d. While depressing the brake pedal without depressing the accelerator pedal, move the shift lever to D and wait for 5 minutes.

(If no DTCs are output, proceed to the next step.)​

e. Drive the vehicle for approximately 5 minutes referring to the following freeze frame data items: "Vehicle Spd" "Shift Sensor Shift Pos" "Accel Pedal Pos #1" "Engine Revolution" "Engine Coolant Temp" "Master Cylinder Ctrl Trq" "Motor Temp MG2 (No2)" "Motor Temp MG2 (No1)"

(If DTC P0AA6-526 is output, stop the vehicle, select park (P), turn the power switch on (READY), turn the air condition system on (Lo/COOL MAX, blower speed HI) and wait for 1 minute. Then turn the power switch off and wait for another 1 minute.)
(If the freeze frame data item "Vehicle Spd" is 10 km/h or less, drive the vehicle at 10 km/h or more.)​

 

You shouldn’t have been able to get past step 2 without INF codes. The later steps were written with the assumption that you used the INF codes to determine the fault area.

It’s not just the model year: the manuals are under continuous revision, and even for model year 2004, the Repair Manual was revised as late as 2017. The changes are substantive; for example, the latest edition of the manual for model year 2006 includes the note I quoted in post #10, which earlier editions lack. For model year 2008, the latest P0AA6 procedure has 30 steps, and for the INF codes 526 and 614 combination, you jump to step 28, not to step 19, and do only three tests.

I think that’s more because the 2006 version circulates (unofficially, I might add) as a single PDF document that people find convenient to use, than because it’s the most complete or current. It certainly wasn’t written to cover earlier or later model years, each of which has its own manual, though the differences might or might not be important for a particular repair.

That’s yet another problem with the old edition of the manual. It was published before Toyota offered the EV converter or transistor set as service parts, so it lacks the “Electric Vehicle Converter” and “Power Module Intelligent Transistor” topics that explain how to replace them, and in the diagnostic procedures, once any problem is found inside the inverter with converter assembly, you’re told to replace the entire assembly, since that’s all that would have been available in the parts system.

You don’t have to look far for examples—in the current Repair Manual for model year 2008 on techinfo.toyota.com, in the P0AA6 procedure, see step 18 for an example of “Replace Electric Vehicle Converter Assembly” and step 27 for an example of “Replace Power Module Intelligent Transistor Set.” Neither of these helps you, of course—for INF 526 & 614, you’d go to step 28, which still says to “Replace Inverter with Converter Assembly” if the megohmmeter test of the frame wire, system main relays, etc., passes. Depending on the results of the other tests, it’s the system main relay, system main resistor, or frame wire, by the way.

 

I didn’t see anything that says to proceed, if you don’t have a way to read INF codes, as though only INF code 526 has been output. Just as later steps require a megohmmeter, steps 1 and 2 require the Intelligent Tester (Toyota’s hand-held unit, now obsolete) or in later editions, the Techstream system.

Standard subscriptions to techinfo.toyota.com start at $20 for two days, during which you can save or print as many topics as you wish, though there isn’t a button or link to download or print an entire manual at once. Many people can also get access to reasonably current versions of the Repair Manual text and illustrations at no charge through public libraries, as I explained on the PriusChat Wiki page.

I’m glad to share brief excerpts verbatim (as in post #10), but posting much more would be difficult to defend when the manuals are available from sources licensed by Toyota.

Steps 28–30 aren’t anything really new; for INF code 614, the main effect of the reorganization is that you don’t continue unnecessarily with tests in other areas. Step 28 is like step 19 in the older edition, with added notes to check the inverter for coolant, water, etc., and to use the megohmmeter’s 500 V setting. Step 29 is like step 22 in the older edition, but you disconnect only the frame wire and system main resistor from the system main relays. (I imagine the authors realized that the battery side of the relays can stay connected, since with the car not in READY, the contacts should be open.) Step 30 is like step 23 in the older edition, but the outcome if the test passes is to replace the frame wire, not to continue with another step.

About the internal parts of the inverter assembly, the examples I gave are the only places in the current P0AA6 procedure that call for their replacement. In step 18 (for INF code 611), if the electric inverter compressor and its cable pass a megohmmeter test, you’d replace the EV converter assembly. Similarly, in step 27 (for INF code 613), if the transaxle and its cables pass a megohmmeter test, you’d replace the transistor set. In either case, you also have to inspect the inverter with converter assembly for “coolant leaks, water intrusion, excessive deposits and damage,” which if found mean replacing the whole thing.

Considering the hazards of high voltage and the risk of damage to the vehicle, I strongly recommend using the actual Repair Manual, not my summary, of course.

 

I'm glad the problem is solved, but in fairness to the repair manual, it's not clear on this record that you really quite did follow the procedure for diagnostics. If you had followed step 2 (read the INF codes), the 614 code would have sent you straight to the section where the frame wire would be the first thing you would test.

I understand you had a reason for not following step 2: if a step says "read the INF codes" and you don't have a way to do that, you're not going to follow the step. Ok, but we can't fault the manual for that.

Instead, you followed the procedure for finding no INF code other than 526, which probably was the next best option if you couldn't read the codes. That sequence of tests did get you eventually to the frame wire, just after a dozen or so other tests that reading the INF codes would have spared you. And when you got to that step you did report:

so you may have been quite close to finding the problem right there, but possibly distracted enough by the other tests in the unnecessary sequence you were following that you didn't focus on running down that lead.

It seems like the other thread you mentioned in connection with the frame wire was Wardtp's thread, but even there it's not completely clear what was going on with your test. Wardtp reported an unequivocal megger test result on the 2005:

The megger test you were reporting in that thread looked like the VC60B+'s "overrange" display, which would represent a passing, not a failing, test. But it seemed like unfamiliarity with a new instrument could have been a factor, and also it's hard to see your exact test setup and procedures over the internet. It would be interesting to see further test results on your old frame wire to see the fault clearly shown.