Prius 1st gen – P3101 & P3191 part 1

TSB EG011-03

This story continues here: Part 2!

Apparently, the following symptoms are a common problem with the 2001, 2002, and 2003 Prius, although this is the first time we’ve seen it here. Up until now, most cars with this problem have been at least partially covered by the 7 year, 70,000 mile California emissions warranty.

The owner will notice the exclamation triangle on the dash, the information screen will display a hybrid system warning icon, and the check engine light will illuminate. When the car is towed to the shop (the owner’s manual specifies “pull over and do not drive” when the hybrid icon is showing), the mechanic will find codes P3191 or P3190 stored in the engine control computer and P3101 stored in the hybrid control computer.

P3191 means the “engine did not start”. P3190 means “poor engine power”. Toyota recommends checking the basics first: air, fuel delivery & injection, spark & timing, compression. They also state incorrect oil level or even incorrect oil viscosity can cause these codes.

P3101 means “engine system malfunction”.

Our first Prius with these symptoms started right up off the tow truck and the customer reported the car seemed to start and run fine, the lights just came on right after starting the car. We checked the oil level and we knew the oil viscosity was 5W30 because we had done the last oil change at our shop. Since the car started and ran perfectly, it seemed unlikely we’d find a problem with fuel pressure, compression, or ignition while the symptom was in remission. Instead, we decided to focus our efforts on the freeze frame data as per the bulletin.

The pictures below document what our scanner showed. A word of warning: if you are working on a Prius with the same symptom and are hoping to find *the* answer, you are going to be disappointed. We are not sure we’ve fixed the car. This story is of the “to be continued…” type.

We have the very latest version of the Toyota software, ordered only a month ago.

We’re doing diagnosis (or so we hope).

Option 1: OBD/MOBD. It might seem like “Enhanced OBDII” would be the better option, after all, enhanced sounds like you’d get something extra, but you don’t. Enhanced will actually give you less information than OBD/MOBD.

The MasterTech is not as smart as the ConsultII, you need to tell it what you’re working on. In this case, not a 1998 4Runner.

Scroll down to 2002

Choose the Prius

Yep. I’m sure it’s a 2002 Prius.

Option 1 – Codes (all), will alert you to codes in all seven systems. You can also choose to check only one system. The only advantage is that it’s a little faster.

Use the standard OBDII cable.

Two minutes seems like a long time when you’re staring at a screen, but it usually only takes 30 seconds or so.

1 of 7, then comes 2 of 7 and so on.

Engine and transmission = NG, which means “No Good” as far as I know. Hybrid Vehicle ECU also = NG. I click on Engine and ECT to start.

Waiting again.

P3191: engine does not start. The TSB focuses mainly on freeze frame data from the HV ECU, so we’ll exit out of the engine ECU menu.

Now we check the HV ECU codes

Code P3101. By the way, any code that does not start off P0xxx is a manufacturer specific code, and is not part of the OBDII standard. It’s something extra added by the manufacturer for use by their dealerships. Starting in 2007, information access may be getting a little better with aftermarket scanners, but that’s another story.

Waiting again.

Freeze frame data for the HV ECU. The inverter coolant temp is actually about double the ICE coolant temp (sorry, forgot to take a picture of the freeze frame data for the IC engine ECU. But don’t worry, I managed to capture all of the “please wait” screens :).

The TSB says INFORMATION 3….204 is what we should be looking for. By the way, no information whatsoever in the manual about this stuff. Modern manuals really need to be about 5000 or 6000 pages (or the electronic equivalent), but most of them are only 500 to 2500 pages. We’ll be relying more and more on central “pattern problem” diagnosis being doled out through TSBs. Mechanics lucky enough to find a one-off problem caused by a body shop or other odd event are going to be hurting.

More waiting after selecting INFORMATION 3….204

The TSB says to record the MG1 TORQ value. In this case it’s 4 Newton meters.

Next we look at EXCLUSIVE INFO3. According to the TSB, it can either be 1 or 0. In this case it’s 1, which means “detected out of gas condition”. The TSB flow chart ends with, “Explain to customer and monitor”. Unfortunately, there is no explanation of how the “out of gas condition” is detected. The fuel gauge was reading 3 bars (about a 1/4 tank). We went to the gas station and filled the car until the nozzle shut off. About 9 gallons. “Explained to the customer” that because the Prius has a sealed bladder type fuel tank the gauge reads inaccurately. We also parked the car on level ground and re-calibrated the fuel gauge inclination sensor in hopes it would improve the accuracy of the gauge. When we were done, our customer “explained to us” they routinely add 9.5 gallons of gas when they fill up, so why would their car run out of gas on level ground when it only needed 9 gallons of gas, besides, Toyota claims the tank holds 11.9 gallons.

We delivered the car about a month ago, and so far we haven’t heard any bad news. This could mean it’s not acting up anymore, or our customer has lost faith and taken it to a dealer (hopefully the former). If you’ve run into the same scenario, and have any experiences or knowledge you think might be helpful, I’d love to hear from you.

This story continues here: Part 2!