Clock & MPG Screen Random Reset? Gas Gauge?

[r mann]

Our '08 is randomly resetting the clock and mpg computer plus the gas gauge reading goes from nearly full to almost empty and starts flashing (there is gas in the tank). Also, a couple of times the car's power button did not work. The car's power came back on after the power button was pushed to turn it off, or pushing the power button would not turn the power on.

These all happen at the same time, when the car is started. (Except for the times the power came back on by itself after pushing the power button off). It has been in for service to take look at the problem twice in the last month. So far they have checked - 12 volt battery connections and fuse box connections.

The car is running fine - mileage is about 50 mpg - no indicator lights have come on and the service department has not reported any trouble code readings.

Anyone else have this problem? Or suggestions on what might be the cause?

[rigormortis]

have them physically remove the battery from the car and do a load test on it to rule it out.

i dunno about the gas gauge

the general rule of thumb is toyota dealers do not like physically testing
the 12 v battery

[rigormortis]

http://www.autoshop101.com/forms/Hybrid13.pdf

that says the dealer can recalibrate the gauge if you have problems with it

[buckeye.mary]

My '08 just did almost the same thing. This morning, the mileage-per-tank counter reset in the middle of a tank, and this afternoon, the gas gauge dropped from 3 pips missing to empty (fill tank indicator came on.) I filled up right away and only had to put in 3.5 gallons.

I hope this is not a symptom of problems!

[Patrick Wong]

Originally Posted by r mann

... Or suggestions on what might be the cause?

My guess is that your 12V auxiliary battery is bad. If you have access to a digital voltmeter, perhaps you could measure the battery voltage when the car is IG-OFF and when it is READY.

You can do this either by measuring the voltage from the dedicated jump start terminal in the large relay/fuse box near the driver's side fender to a bare metal point on the body; or else finding the battery in the right-rear corner of the hatch and measuring the voltage at the battery terminals.

When IG-OFF, the voltage should read ~12.6V several hours after the car was last driven. If the voltage is much lower than this, this is evidence that the battery needs to be charged or is bad.

When READY, the voltage should read ~13.8V which shows that the DC to DC converter is working properly.

[r mann]

Update on problem -

First Dealer visit - they traced the problem to the fuse block and "fixed" the connection.

Second Dealer visit - this was a problem that took a few days to solve. Because they had just worked on the fuse block they looked at other areas. Everything seemed OK, but the resets kept happening. It appears that there was a bent/loose pin in the connector at the fuse block that would open when the car was "cold" from sitting - but would close after the engine compartment warmed up from running the engine or sitting in the sun. So far (less than a week) it appears to have been fixed. All three (clock, mpg screen, and gas gauge) resets seem to be related to power interruptions from the loose connection.

[priususername]

Originally Posted by r mann

Update on problem -

First Dealer visit - they traced the problem to the fuse block and "fixed" the connection.

Second Dealer visit - this was a problem that took a few days to solve. Because they had just worked on the fuse block they looked at other areas. Everything seemed OK, but the resets kept happening. It appears that there was a bent/loose pin in the connector at the fuse block that would open when the car was "cold" from sitting - but would close after the engine compartment warmed up from running the engine or sitting in the sun. So far (less than a week) it appears to have been fixed. All three (clock, mpg screen, and gas gauge) resets seem to be related to power interruptions from the loose connection.

r mann, thx for your message. been having similar problems with my clock and mpg reset, and the car powering on immediately after turning it off. fortunately, no gas gauge problems. Just curious, did the dealer say where exactly the loose pin was located? Do you have any aftermarket modifications like EV Mode?

I've checked the voltage on the 12volt using the onscreen display check and i'm at 14v in ready mode. So, i'm ruling out that its my battery.

[Rokeby]

Originally Posted by priususername

... I've checked the voltage on the 12volt
using the onscreen display check ...

priususername,

I've been looking for the directions to get the 12V battery voltage up on
the MFD without success.

Could you post how to do this or provide a pointer to where it is?

[jdenenberg]

Originally Posted by Rokeby

priususername,

I've been looking for the directions to get the 12V battery voltage up on
the MFD without success.

Could you post how to do this or provide a pointer to where it is?

You need to put the MFD in it's maintenance mode. First from accessory mode (to get the battery voltage with no charging current and with a low current load) hold the dashboard INFO button down and flash the parking lights 3 times. Press the on screen menu button and then signals. The Battery voltage should read a little above 12volts.

Now press the POWER button to put a larger current load on the battery. The voltage should drop a little, but stay above 12v.

Now hold the BRAKE down and then press the POWER button to go into READY mode. The voltage should jump to just below 14 volts as the charging system turns on.

Powering down your Prius puts everything back into its normal operation.

JeffD

[Rokeby]

Originally Posted by jdenenberg

You need to put the MFD in it's maintenance mode. First... etc, etc, etc..

JeffD,

Thank you sir.