Problem SOC levels on 2002 Prius

Are these percentages the actual battery SOC, or percentage of the bars on the MFD?

 

I think Patrick Wong has had to deal with traction battery problems in the past. If I remember correctly, rapidly changing SOC was one symptom and consistent with a weak traction battery.

Bob Wilson

 

Since the OP is talking about 25%, 50%, 75% and 100%, I assume he is referring to the presence or absence of the four bars on the SOC gauge. This does sound like the traction battery is about to give out.

Is the car still covered under the 8 year / 100K mile warranty? If so you might encourage the battery to die sooner vs. later, by stressing the powertrain over mountainous terrain (like driving north on I-5 to Tejon Pass at a rapid pace, or taking a trip to Lake Arrowhead, etc.)

I don't know about the clicking sounds, might that be coming from the braking system? Try repeatedly pumping the brake pedal while the car is READY and stopped, to see if the clicks happen then.

 

I'm 99% sure that warranty applied to the 2004 and later Prius. Patrick Wong would be the expert. However, we have seen Toyota 'do the right thing' and honor battery warranties in the past.

It makes sense to 'get it on the record' at your local dealer. You might ask them to:

Perform the P3011-3029, "Battery Block # Malfunction," which entails a controlled discharge and charge monitored by the TechStream.
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Unlike earlier years, there are options including Re-InVolt and owners who have rebuilt their traction battery packs. I helped on one traction battery replacement: two people, 4 hours and the owner paid $1,700 for the swap.

Bob Wilson

 

Try A quick check before anything else -measure your 12v battery with a volt meter while in ready mode it should be 13.8v or so, if it's lower than that many things can cause this including the inverter, the traction battery, even the 12v battery itself if it has shorted cell(s). If the 12v system voltage drops too low, it'll cause all kinds of weird readings and false warnings from the electronics ref levels changing. The latter is of course if the 12v drops below say about 11.8v and lower. Just 2c..

 

The 10 year / 150K mile traction battery warranty (for CA and other states adopting CA regs) started in the 2004 model year because that Prius model is rated AT-PZEV. Earlier Prius do not have that rating.

If your car does not show any warning lights, then no one at your dealer will care (for warranty purposes) whether your SOC gauge shows 0%, 25%, or 100%. If there are no warning lights then no DTC will be logged; and if no traction battery-related DTC are present then no warranty action will be taken with your traction battery.

If you wish to pay for the diagnostic test that Bob mentioned, it's up to you. However even if the test shows a marginal result, as long as no DTC is logged the dealer won't take any warranty action. Hence I don't see the point of paying for the test.

Rather, it might be better to see if you can drive the car hard enough to get the hybrid vehicle or traction battery warning icon in the MFD to appear.

 

Since you've noticed this happen intermittently over the last 3-1/2 years, I doubt that the traction battery is the problem. However since no warning lights have appeared, your car probably doesn't have any logged DTC to help you figure out what is the problem.

Maybe the traction battery ECU or hybrid vehicle ECU has a random glitch that appears infrequently?

 

"Big Hand"?

There is a known weakness in the NHW11 accelerator that dirty contacts can lead to a loss of acceleration. I understand it can be a brief event although most have described it as lasting longer. Usually it throws a code but some have claimed it can occur without a code.

The stock accelerator from Toyota is ~$500. You can refurbish it yourself following Doug's excellent instructions. I do it by swapping out my accelerator, your replacement, and then I test and rebuild the part you return.

Bob Wilson

 

Good. But does that mean the battery is at peak reading?

 

If no DTC was logged then it's going to be tough to diagnose your car's problem, especially since the problem happens so infrequently.

You could:

1) sell the car if you feel it is unsafe when the problem happens

2) buy a salvage traction battery ECU and hybrid vehicle ECU, and install both (in essence, throwing parts at the problem.) No assurance that will help, though.

 

I agree with Patrick. Could you give us an idea of how frequently this occurs?

Bob Wilson

 

Hi Bob,

4 or 5 incidents, over 3-1/2 years.