ECU malfunction Codes at 159,000 miles / Service

Thanks for answering so quickly, Patrick! Oddly enough, no other warning lights were triggered. That's what has me stumped on this one.
Brakes are functioning normally and have had no detectable issues.

The gas cap O-ring looks fine remains firmly attached - no distortions pliable. Fuel tank is rust free. No evidence of any leaks (fuel or otherwise) when parked. No evidence of fuel vapors either inside or outside the car. Nor any CO emissions leaking into the cabin. I would guess that if the manifold's hairline cracks had opened up, there would be fumes leaking into the cabin area. The muffler is new (no bearing on the codes - just a mention) and the original exhaust system including the cat conv was inspected thoroughly prior to installation and showed no sign of loss of integrity or weakness around the welds, casings or pipes. (Although the cat can fail and deteriorate from the inside). No rattling or other issues within the exhaust system. Car runs quietly and smoothly and behaves as expected. Excellent, I'd say for its age and mileage.

 

The morning after...

Woke up to moderate snowfall and decided to start the car (to see if the CEL was still lit) before bothering to disconnect the 12v. Results? NO CEL.

This is another good news/bad news situation. The good news, of course, is that the CEL has turned off on its own. I am grateful that (with the current mileage) the car seems to be running fine. The bad news is that I have no idea why codes come and go as they do on this car. I will disconnect the 12v when the weather improves to clear the codes that were stored as a result of ???

Is it unusual for the Prius to be randomly throwing DTCs or is it that this vehicle has a strange 'quirk'?

I will see what happens today after driving around and report back. The car does roughly 700 miles a week - 120/day M-F and about 25/day on the weekend.

 

True. That is why I am monitoring the situation. Cleared the codes and the CEL has remained off. We will see what the coming days, weeks and months.

 

Update: Went out to dinner last night and now the airbag light is illuminated. No specific cause although the temperatures here remain well below 0 F during the day and have only climbed to the upper teens during the day. The CEL has remained off and the car still performs as it should.

 

No, I have not retrieved the DTC yet... The light went out on my way home tonight.

The car was in an accident back in early 2008 which was not a front end collision. The car only had about 34,000 miles on it at the time. I swerved right to avoid a driver heading toward me in the wrong lane as I approached the top of a hill. Damage was confined to the left wheel area, the front fender and door. Nothing at all on the front bumper or in the engine compartment. Shortly after the repair, the SRS light illuminated. The dealership corrected the issue at no charge since the car was still under warranty.

In 2011, after 3 years without trouble, the SRS light illuminated again. After a few months (with no reason) it shut off.

As of now, there are no warning lights displayed and "all is well" or so it seems. I will know in the morning. The car is still riding and responding as it should.

I don't want to take it to a dealership at this point because their guess is as good as mine as long as codes are being logged intermittently. At 220,000 miles, I would rather wait until there is a detectable problem with the vehicle's function. I can't trust the warning lights. However...If the triangle of death should appear, I will take that one seriously!

 

Here we are nearly 2 months since the intermittent codes and all has been well. The car easily passed inspection on February 28th at 224,659 miles. I am guessing that the low temperatures are what triggered the airbag warning light to illuminate as I had the same issue with my 2003 Highlander (76,000 miles) in the extreme (-27F) weather. The airbag warning light on the Highlander, however, only remained lit until the vehicle was at operating temperature. This winter has definitely been brutal.

 

Arrgh! Here we go again. CEL back on at 228,000 miles. Car rides fine and no other warning lights at this time. Oil level and coolant levels are where they should be. Gas cap o-ring is fine and cap is snug. Hybrid battery is doing what it should given the mileage. I can not imagine how much money I would have wasted if I ran to the dealership every time an error code was logged.

However, I was a bit concerned when I checked the coolant. It was not pink. The color resembled more of a pale orange. I can't understand how this could be if the hybrid cooling system is a separate loop than the engine cooling system. Especially since the water pump was replaced for the first time last summer and I was charged for a gallon of SLL coolant. You would think that the engine coolant would be pink - correct? Since the Hybrid cooling system's fluid is older, I would (maybe) expect a deviation from the norm but both? The same? How could that be?

This is not the first run in I've had with this dealership. I believe that the old coolant was dumped right back in the system when the water pump was replaced.

Since the weather has improved quite a bit, I plan to wait it out a few days to see if the CEL goes out on its own. Patrick: I have a sneaking suspicion that the oxygen sensor is the culprit. I'll find out once the codes are cleared this weekend and the CEL illuminates again. If so, a quick and easy fix.

My question: Should I be concerned about the color of the SLL that's circulating through the systems?

At this point in time, I am wondering how long the car will last. The car will be 10 years old on November 4th. I am torn between parting it out and selling it as a whole. (The leather seating and all trim - Bisque - including the original carpeting and floor mats are in mint condition - always covered). Believe it or not, the engine is still tight and I only add an ounce or 2 between oil changes every 5000 miles with Mobil 1.

The 2016 Prius is on the horizon and I was hoping that the car would hold out until the new models are released.

 

Thanks Patrick - I have an antifreeze tester and will get to that this afternoon!

 

Here we are in June. I waited to see exactly what would happen if I DID NOT clear the codes by disconnecting the 12v. At the last reading on April 15, codes were C1311, P0456, P0137. Exactly 2 months later (June 14), the engine light went out on its own and has not come back on (so far). Throughout the entire time, the car has behaved normally, gas mileage remains at 45mpg+ and the current mileage is approximately 237,000mi. Again, this is very unusual but something that I have grown accustomed to as just another "quirk" with this particular vehicle.

Back to the coolant issue: The dealership took the car in right away and corrected the problem. New coolant installed. I am wondering at this point how long the car will last. Waiting for the 2016 Prius to debut in December.

 

I can't imagine how the dealerships would have preyed upon someone who would bring it in each time that light would illuminate. Better off to sit back and observe than have my wallet drained... especially if the car is not exhibiting any outward signs of trouble!

 

...that is if the parts are replaced at all! Don't get me going on that one. I have literally caught dealers charging for what was not done!