Master Warning, ABS, (!), and Hybrid Vehicle Warning icon

[Patrick Wong]

We're currently in Green Valley, AZ; south of Tucson. Drove ~500 miles yesterday from OC in the 2004 w/76K miles, no problem. Today we drove up to 5,400 ft elevation. On the way down, the Master Warning light, ABS light, (!) brake light, and hybrid vehicle icon in the MFD all appeared. The brightness of the instrument panel and MFD illumination dropped down to the level when headlights are turned on, although the headlights were off.

I have no tools or test equipment in the car. After some thinking, I decided to drive to the Toyota dealer ~30 miles away (Precision Toyota.) The traction battery SOC started at 7 green bars and dropped down to 5 blue bars during this drive. The traction battery fan was on at high speed. The MFD showed arrows when power flowed from the gasoline engine to the wheels. However it did not show any regen arrows nor did it show power flowing to or from the battery.

The driveability was impaired because the engine ran at all times and acceleration was very slow, so I had to get out of the way of traffic behind me from time to time. I did manage to get up to ~65 mph while on I-19 (speed limit is 75 mph.) Then we had to go through I-10 which has several Tucson city exits blocked. Then it turned out the Magellan GPS had the wrong address for the Toyota dealer so I had to call the dealer receptionist to get the right address. However we finally got there, dropped off the car, and rented a Yaris.

My usual guesses as to the root cause would be an inverter coolant pump failure or a traction battery failure. However since I was able to drive an extended distance without the car shutting down, I think the inverter was running at least well enough to keep the 12V bus alive. The battery SOC was not jumping up & down wildly, so that causes me to rule out a battery failure.

I am now thinking that maybe the inverter has a weird problem that does not impact the DC to DC converter, or the hybrid vehicle ECU has a problem. Anyone have other guesses, please chime in.

I hope to hear from the service writer tomorrow regarding diagnosis, etc.

[Shawn Clark]

Did the traction battery fan stay on at high speed the whole time? If it did then I wonder if it is throwing some sort of erroneous high temperature reading for the battery pack? Perhaps going into a high temperature protection mode that prevents transfers to/from the traction battery?

The fact that it continued to misbehave and stayed in "limp along" mode suggests to me that it wasn't something as simple as a battery cooling problem. If say the traction battery ducts were plugged (rodents, etc), the battery got hot, and the fan ran (but couldn't move any air because of blockage) then I would expect it to cool down after a time in this mode, but it sounds like this never happened.

[hobbit]

Wow. I guess it can happen to the best of 'em. In the long run I bet
it'll turn out that that Prius chose the wrong guy to mess with, as
every detail of ferreting out what's wrong will likely hit the net...
.
Was the inverter pump *running*? That's easy to check..
.
_H*

[FL_Prius_Driver]

The battery would have been subject to an much higher than normal heat load on hills in the hot southwest. Once you started down the hills would have been charging the battery to the max SOC and that would most likely made it as hot as it was going to get. Were you in B or D mode?

I would expect the inverter heat load would be hardly any different than normal, since all the MG1 and MG2 current flows through it regardless of battery condition.

[dogfriend]

What was the ambient temp? I'm thinking pretty hot. Could you possibly have a bad 12v battery? I always seem to lose batteries during the summer, sometimes with little or no warning.

[tochatihu]

Good luck Patrick. I know you've been on tough Prius trails before.

[efusco]

Were you able to get them to hook up the tester before shutting down or did you have to go through the usual rigamarole? And, honestly, I'm shocked that you didn't have at least a Scan Guage with you.

[bwilson4web]

A thread worthy of subscribing.

GOOD LUCK!

Bob Wilson

[jayman]

Originally Posted by Patrick Wong

I have no tools or test equipment in the car.

Well, I got to this party a little late. I sent you a PM.

[Patrick Wong]

Thanks for the comments.

No Scan Gauge, as I question its ability to retrieve DTC generated by ECUs other than the engine. Jay suggested trying to retrieve blink codes; however I believe that is limited to a very small subset of DTC. In any event the car is now at the Tucson dealer and I haven't yet received a diagnosis.

The 12V battery is original. No problem starting the car, the warning lights came on ~20 minutes after we started our descent from Madera Canyon (a very nice hiking and birding spot, BTW.) I was using D until I saw eight green bars on the traction battery SOC display, then moved to B. Once the road became less steep then I returned to D.

The battery fan was running much more than normal. I had the A/C running, trying to keep the battery cool. Ambient temps in the high 90s F.

We are planning to proceed on to Sedona tomorrow with or without the Prius. If the car isn't repaired then I'll have to return to Tucson next week if/when it is repaired...