Clearing P1128, P3191 Codes

Results of troubleshooting and repairing 2003 Prius P1128 & P3191 codes

These codes appeared a week or so prior to the vehicle finally slowing down and eventually stopping. I had cleaned the throttle plate about a month earlier and cleared a previous code. Vehicle ran normally until the last situation where the P1128 and P3191 set.

After some research I cleaned the throttle plate again and also removed and cleaned the MAF. If you deside to use this procedure be SURE to use an approved MAF cleaned. I used CRC from Walmart along with their throttle plate cleaner.

During this process I replaced the PCV valve as I assumed it had not been done in “forever” That was a chore in itself.

After completing these task, I cleared the P1128 and P3191 codes and restarted the engine. Vehicle ran a short time then engine shutoff and codes returned. I tried this procedure several time with the same result. Frustration was beginning to set in at this point. At this time I desided to take a break and wait until the next day.

Next procedure began with clearing the codes, disconnecting the 12V battery and attempting the restart the vehicle. The same results as previous returned. I attempted this several times, each time the remained the same.

At this time I decided to disconnect the MAF and TPS sensor connectors and reinstall them. Do this just to to ensure good contact. After reconnecting the the MAF and TPS I disconnected the 12V battery and waited about 30 minutes to reconnect it. Started vehicle with accelerator pedal depress about 40%. Engine restarted and continued to run. Held accelerator depressed for a short time (about 90 seconds) then released it, engine continued to run, No codes or red triangle, and all systems seemed normal.

Drove vehicle about 10 minutes without any defects.

For those courious both batteries were good during all these test and operations. 12V battery reads 12.2V – 12.4V OC and 13.47 with KOER. All main cell on HV battery between 16.03 – 16.3 KOER and 15.96 -16.02 KOEO.

I realize this is lengthly but hoped it would help anyone confronting a similar issue. I have only had this vehicle since September and have had a few small issues: Inverter pump, P0420, P1128, P3191 etc.

I have changed engine oil and filter, transmission fluid, inverter pump and coolant. The vehicle had 221,480 when we purchased it, so was expecting so issues. Still learning as I go. Love the challenge.

Best tools in the box are Mini VCI w/Techstream, Fluke 87 III and a Pico 212 dual trace scope.

Hope this helps folks.

 

Second day, so far no lights or codes. Vehicle appears to operate normal. Will keep you’ll posted.

 

I have Repair Manual for Gen 1s on CD and a paper manual of 2003 wiring schematics. Found schematics are a must on any newer vehicle. Wish I had some info on the operational strategies of the systems and how they interface. Give me a 6 months and I'll have these things figured out. Still not sure why it took many recycles of clearing codes and 12V disconnect to completely clear defects from system.
We've had fairly cold weather lately (zero and below) and this could have affected the vehicle, but battery voltages stayed well within limits so I have to assume that was not the issue.
Love this forum, it has been a great aid to this novice in the learning process.

 

It's been a week since repair and all appears well. The acceleration has also improved. Cleaning the MAF helped that, I'm sure. Weather here has been up and down, but hasn't effected vehicle. Still having issue with the MFD blinking but appears to function as designed. Will see how that plays out, but I'm sure it won't fix itself. My guess for now is it is in the display itself. Does anyone know if all Gen 1 displays are interchangeable. This car has navigation. Thanks to all for the data this site provides. Peace.

 

I have extensive background in both aircraft and automotive maintenance since the 60's. Also developed and taught an Automotive Technology program @ community college. Master Tech with an L1, but this area is a learning experience for me. I'm also an iatn member. I'm retired but can't seem to give it up. I purchase the Prius to replace a '91 Civic we owned. Wanted to have one that many miles and age to use as a test bed. As my experience was very limited with hybrids, this seemed the best way to improve my understanding. So far I'm at least up with it but I think there is much more here for improvement. In this case I am a novice. Hope to post info as I cross and solve different concerns as it may help others. Sorry this is long, but you asked so here is some of my background. Peace.