The Mysterious Prius Warning Light Syndrome (and other adventures)

I have this same issue. Lots of error codes; none legitimate. My inverter coolant pump is not the problem. When I jumper the relay, the pump runs just fine.

Issues include suddenly dim headlights, missing lines across speedometer numbers, cruise control turning off, AC giving out (with and without "Air Conditioner Off" warning on console), engine warning light, odd circle warning light, and Red Triangle of Death.

Can drive through most, but parking brake light coming on, ABS warning light, squealing dash, and car applying brakes is a show stopper.

In deep south Texas and headed for Mexico. Far from not-so-Sweet Home Chicago.

Internal check of 12V battery shows OK. Disconnected and resting to cool everything and reset whatever computer brain is failing.

This electrical gremlin is in some module (PCM? ECM?) and driving lots of sensors nuts. Really missing my analog 2000 Honda Civic at the moment.

Any prompt suggestions will be extremely appreciated.

 

List all the trouble codes that you read, and you may get some help to fix the problem.

 

^^^^ This. Once we know what trouble codes the car is reporting, we'll have a better idea which ones are 'legitimate' or why you might think they are not.

 

P0A93 - inverter cooling performance
P1121 - failed coolant flow valve
P1116 - inverter coolant warning
P2238 - O2 sensor

Didn't have a chance to read brake light, ABS light, etc. codes. Just desperately cleared them with ODB reader while at speed.

Also forgot to mention that displayed charge of hybrid battery changes wildly. One moment it will be double green bars. Then I'll get so many codes that I stop, turn the car off, back on, reset all the codes, and the hybrid battery will display 2 or even just 1 red bar of charge. I also occasionally get the 'no display' issue and must get it back on with the button + headlights on/off + door open trick.

Had to finish yesterday's leg after dark. Headlight dimming was cyclical, with error codes arriving during both normal and dimmed illumination. Unplugged USB charger from 12V socket, turned off vent fan, turned off radio, and turned off console display = minimal power draw. (No headlights was not an option.) The frequency and number of codes appreciably dropped, but not to zero.

Arrived in Monterrey, MEX to a full-blown, Christmas tree dash of lights. Every console light at once.

Will retighten 12V battery's connections, but that's a super-longshot. More likely that some wiring harness is failing or the ECU got burned when my catalytic converter was stolen… twice!

I can replace the inverter coolant flow valve and the 12V battery, but that's a fair amount of time, effort, and money to piss away, the problems persist, and that time, effort, and money not be refundable.

 

P1116 has nothing to do with the inverter coolant loop. It is involved with the CHRS coolant switching valve (part of engine preheat).

 

Trying to simplify or paraphrase what trouble codes mean will often lead to missed diagnoses. For example, P1116 doesn't mean "inverter coolant warning", it means one of these things happened:

• Temperature change during hot coolant recovering: 3℃ or less
• Difference between CHS tank outlet temperature and engine coolant temperature during hot coolant recovering: More than 25℃

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Similarly, P1121 isn't telling you "failed coolant control valve", it's telling you one of these things happened:

• Water valve position sensor output voltage: No change despite the ECM sending a valve control signal or slow response
• CHS tank outlet temperature sensor output: 60℃ or more (when hot coolant recovering starts)
• CHS tank outlet temperature sensor output: No change despite the hot coolant is recovered

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(Bless the Japanese-English translators, they do their best.)

P2238 means one of:

• AF+ [from the air/fuel ratio sensor] is 0.5 V or less for 5 seconds or more
• A/F sensor admittance: Less than 0.022 1/Ω

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(You don't see "admittance" every day; it's the inverse of impedance, which would be measured in Ω. In the straight DC world, "Less than 0.022 1/Ω" means the same thing as "More than 45ish Ω", which might be easier to measure. But I'm not sure A/F sensors are fed straight DC; if they're not, complex math is involved converting admittance to impedance.)

The benefit of looking up what the codes really mean is that it gives you strong clues what you can check to see what's going on, before just pissing time, effort, money away taking stabs in the dark. Shorthands or fortune cookies for the codes don't help you that same way.

 

I'm not reading a suggested solution in any of that. I'm also beginning to believe that the coolant control valve is the issue.

Just checked the car after a cool night. Radiator fans run (at least the engine side one does; no view of the inverter side one from above the engine bay and I don't have jack stands with me). Both coolant reservoirs are at full line. AC (on MAX COLD) blows cold right away. ODB reader gets a P1121 code with no warning lights on dash. No other codes. Jumping relay, the inverter coolant pump audibly runs, but there is no visible movement in the inverter coolant reservoir fluid. Definitely no swirling. Seems like fluid is not passing through the coolant control valve.

Hybrid battery again shows 2 bars of red for level. Arrived with 2 bars of blue. Either something is draining the hybrid battery while parked or that's a separate faulty sensor / control module issue.

 

The coolant control valve is part of the engine (ICE) cooling system. It directs engine coolant into or out of the the Coolant Heat Storage tank (thermos tank in the left fender). It also affects ICE coolant flow through the heater core.

The control valve has NOTHING to do with the inverter cooling system.

Posted via the PriusChat mobile app.

 

^^^^ This.

Fair enough, because what I was posting was just what the trouble codes tell you, and what the codes tell you is never a suggested solution. They only tell you about specific things a computer in the car saw. (Which, when you pause and think about what is and isn't possible, makes perfect sense.)

What a human has to do, after getting the codes to know what the computer in the car saw, is start answering the question "what could have made it see that?", by starting to check the things that could be involved. For different people with different cars giving the same code, the culprit won't always be the same. That's why even with computers and codes, there is still good honest work for the human to do to fix the car.

The main thing I was getting at in #26 is: if the human starts with a bunch of vague/wrong paraphrases of what the codes mean, the human's good honest work may go down a lot of dead-end paths.

 

Found plenty of people who have experienced the same cluster of warning codes and lights from a Gen2. No clear cut solution.

I'll be replacing the ECM as soon as possible. If that doesn't resolve it, I'll move on to the next least expensive module replacement as it's clearly not that my coolant diverter valve, coolant pump, coolant temperature sensor, headlights, dashboard, and ABS system have all simultaneously failed.

That brings up another question. Does the ECM for 2007-2009 require VIN flashing? I know that the 2004-2006 ECM, which is different, does not require flashing. That doesn't answer the 2007-2009 question either way.

 

You need to concentrate on fixing the P0A93 trouble code. Your inverter is overheating and then it goes into limp mode.

Replacing the ECM is probably not going to fix your problems.

 

That'll be because, as mentioned earlier, there's no reason to think the original cause of a "cluster of warning codes and lights" in one car is going to be the same as in another car. In each car, the human has to do the work of understanding what the codes are saying the computers saw, and then work out what made the computers see that, and then fix whatever that turns out to have been in that car.

That's kind of straw-man-ish; there isn't anyone here who has suggested (nor do the codes you've listed suggest) that all of those things simultaneously failed.

But you do have a code about the inverter cooling, and two codes about the engine cooling, and a code about an engine sensor. Your headlight/dash symptoms are consistent with lowered voltage when the DC/DC converter protects itself from overheating, if your 12 V battery is at all questionable (or if you keep driving long enough, however good the battery may be). The two codes about engine cooling could easily share a common cause (the CHS outlet temperature reading figures in to both code trigger conditions).

You haven't listed any brake system codes, but I would encourage retrieving those the next time those lights are on, and adding them to complete the picture in this thread. If your scan tool will not show them, you can get them this way:

Blink (a/k/a Flash) Codes – How to. | PriusChat

 

Just to reiterate what has already been said, all you can know from a light on the dash is that the system to which that light is related is signaling that there is message information (error code) to be read. For each light, there could be tens or hundreds of possible errors. Given this, there can be no clear-cut solution just from looking at the lights on the dash. This is why we're so insistent on getting the actual code(s) that your car has.

Blink (a/k/a Flash) Codes – How to. | PriusChat