Help ICE wont start, Comm buss Down after Cat stolen/replaced

Nice to see Techstream connecting. Any DTCs shown via the Health Check?

 

You've written "the ECU" a lot here, but ECU (electronic control unit) is a generic term and the car has about a dozen of those. From your attached photos, I think you mean "the ECM" (engine control module), which is the one ECU whose job is to control the engine (and pretty much the one ECU that has its own three-letter name).

I also see a P0A0D in your screenshot, about the safety lockout circuit. As long as you have that code, you can be sure the HV ECU will never bring the high voltage online. The usual suspect is that the handle on the battery service plug has not been pushed all the way to its final home position where it completes the lockout circuit.

As the reported communication issue is with the ECM (and it's pretty well confirmed by Techstream not being able to reach the ECM either), you definitely have to figure that piece out. Have you clicked the snowflake ("freeze frame") icon in Techstream next to the U0100 code? You should be able to find an INF code there, maybe 211, 212, or 530, that will reveal more about the U0100 condition.

Have you obtained access to the Repair Manual and the Electrical Wiring Diagram? That's where you'll find information helpful for pinning down the cause of the U0100. You'll find useful testing info both in the workup section for U0100 and in the whole dedicated section for "CAN communication system", and the wiring diagram is the last word on actual connector pin positions and wire colors.

 

So now, the two battery power feeds to the ECM are pin 4 (B+, fed by the EFI fuse) and pin 5 (+BM, fed by the ETCS fuse). Both are in the underhood fuseblock.
Hope you figure this out- however it was mentioned that you should check all fuses to see if one blew due to loose O2 sensor wires possibly shorting.

Posted via the PriusChat mobile app.

 

Could you post photos of the relays and how they are wired?

Some reason to think them stuck closed there must be.

 

Nothing jumps out at me in the photos. Darn.

I am not sure exactly how the HV ECU does the stuck-contacts check. The Repair Manual does explain that when shutting down, it opens SMR2 first, then SMR3, and "checks that the relays have turned OFF properly."

There don't seem to be any local voltage-sensing connections on the relay outputs there, and there wouldn't have to be, because the other end of the frame wire is in the inverter up front and there are certainly voltage sensors there.

But also there are capacitors there, with an expected bleed-to-safe-voltage time around 5 minutes. I'm pretty sure the ECU makes its "did that relay turn off or not?" judgment faster than that. I don't know if it is somehow just looking for the right slope of the decreasing voltage across the capacitor, or if it is doing something clever with recognizing the "short wave" (hee hee) that the battery ECU superimposes on the battery output. If it were only looking at voltage slope, I'm not sure how it would detect the opening of SMR3 anyway.

This might be my first time sitting down to wonder, exactly how do they do that?

I wonder if @Elektroingenieur knows.

At the corner of your battery where the car's frame wire enters, those two cables pass under that shiny foil-y looking clamp with two nuts. Is that tightened down securely over the cable shields of those two cables? Hard to see in the photo.

I'm pretty doubtful that could be a cause here, but I'm kind of grasping at straws.

 

I was thinking something lingering, but then I thought you mentioned clearing and having the P0AA1 and P0AA4 come right back.

 

Two things I noticed is 1) the repair manual does not seem to document the P0AA1 INF code 224 or 226, which is what your freeze frame data shows you have. 2) The repair manual as the very first thing for both P0AA1 and P0AA4 says to 'Refer to DTC P0AE7 (INF 224).'

The inspection procedure P0AA4 is short and sweet. If the information (INF) code is present, replace the No. 3 system main relay. The replacement procedure for the No. 3 system main relay is on page HB–124. Inspection of the No. 1 system relay is contained in the inspection procedure that starts on page HB–125.

I don't know if that helps any.

 

Replacing the relays would be easy enough, money aside, but still, if a meter has flat-out shown they ain't stuck closed, it's hard to see what the car's going on about. It would be frustrating to go through the replacement and still be back at square one.

I had not caught that! Interesting.

Flipping through a Gen 1 repair manual, just for the fun of it ....

Back in Gen 1, all main-relay issues were grouped under a single DTC, P3115. Toyota had to put it in the manufacturer-assigned P3 space, because SAE had not yet assigned any standard DTCs for hybrid system batteries and relays. So Toyota just assigned one code P3115 for anything to do with the main relays, and it was up to the INF codes to tell the whole story.

P3115 had INF codes 224–229 for problems on the control side of the relays (the coil drives), and 231–233 for problems with the contacts (stuck closed). 224 would mean SMR1's coil drive was open or shorted to +B, 225 that it was shorted to ground. 226–229 were the same for SMR2 and SMR3, respectively.

231 would mean the + output was stuck closed (which might have SMR2 or SMR1 as the cuplrit), 232 would mean the − output stuck closed (SMR3), and 233 would mean both the + and − outputs are stuck (and still I struggle to get just how the ECU tells all these cases apart).

Then Gen 2 came along, and by that time SAE had assigned standard codes in P0 space for hybrid system relays, and there wasn't just one anymore. P0AA1 was assigned for a + relay sticking closed, P0AA4 for a − relay sticking closed. For the control sides, SAE assigned P0ADB/C for a + relay coil drive shorted low or high/open, respectively; P0ADF/E0 the same for a − coil drive, and P0AE6/7 the same for a 'precharge' (Toyota's SMR1) coil drive.

It looks like in the Gen 2 firmware, Toyota keeps the same INF codes used in Gen 1, and just deals them out into the new SAE-assigned DTCs:

	INF	SAE DTC	fortune
1	224	P0AE7	SMR1 coil drive open or +B short
2	225	P0AE6	SMR1 coil drive ground short
3	226	P0ADC	SMR2 coil drive open or +B short
4	227	P0ADB	SMR2 coil drive ground short
5	228	P0AE0	SMR3 coil drive open or +B short
6	229	P0ADF	SMR3 coil drive ground short
7	231	P0AA1	+ contact stuck closed
8	232	P0AA4	− contact stuck closed
9	233	P0AA1	+ (and −) contact stuck closed

Apparently SAE didn't assign a code to mean + and − contacts stuck closed, so Toyota deals out both 231 and 233 to P0AA1.

Maybe they just didn't get the dealing-out quite right? If the INF codes showing are 224 and 226, how do the control wiring connections plugged in to SMR1 and SMR2 look?

 

That makes a lot of sense. I was wondering if it was something like that.

So would you say the OP needs to do the diagnostic for P0AE7-224 as mention right at the start of both P0AA1 and P0AA4?

 

I'm not sure that their "refer to P0AE7" in those places meant anything much more than "that's where we put the circuit diagram and the (woefully vague) description of how the stuff works".

But I am kind of thinking that if 224, 226, and 228 are the INF codes present, it might be a mistake in the firmware that P0AA1 and P0AA4 were set for those, and that instead the plan was supposed to be that those INF codes would be mapped onto P0AE7, P0ADC, and P0AE0.

Given that those represent open-circuit (or +B short, but let's start simple) for all three relay coils, I would first be casting a suspicious eye on that four-pole white connection to the mini-harness for all three relays. It appears connected in the photo, but I don't know how much I'd bet on it.