Hello All, ECU IG fuse & IG2 fuse block: Putting 12v to it starts dash lights and the lights start blinking But key press doesn't start car Where does the power to the transmission computer come from? HV ECU... no power Transmission ECU... no power ECU IG fuse... no power Can't read codes from the above ECUs, only the body ECU and it gives codes B2287 & B2289. I replaced the PSC ECU and the car started once. Now any replacements don't start the car. Wires and fuses are fine. Relays may all be fine. They work and were checked and swapped and still work.
What scantool are you using? A Gen2 Prius has 15-17 ecu's, how many ecu's respond (can talk to your scantool) on your car? Do you have a copy of the service manual and wiring diagram? Perhaps a place to begin would be to backprobe the AM1 and AM2 (battery power- pins 12&33) , ground (pin 6), and LIN1 (BEAN communication bus, MPX1 & MPX2, pins 7&24). Measure what voltages are present when the ignition power should be ON. Posted via the PriusChat mobile app.
The voltages are fine 11-12.5 volts. My IG1 relay drivers side junction box is pink. Should those be red? Maybe it was replaced. So the Techstream showed can bus problems (highlighted red) but read the codes with no blue or asterisk ECUs. A snap on odb2 reader could not get anything from the HV ECU or the Transmission ECU.
Can you post screenshot of the Techstream health report (system scan?) Were the MPX1&2 at 11-12V? What about the ground pin? Posted via the PriusChat mobile app.
Mytech stream doesn't go that far into detail but all pins were tested at the psc ecu and they all had 12.5 v.
power train control module under glove box by ecu has its own power fuse under the hood, here is how i know Here is my tranny horror story, it might help someone, same issue, wouldnt go into gear, eventually we were stranded. I will cut the long long story short, after lots of messing around I came to the conclusion that the power train control module was bad, got one off ebay and was then told the dealer had to program it, then was told, no, turn the car on with a battery charger and leave it and it will program itself, and that worked, for a few days, then the problem returned. I went over the schematics and found that the main 12 volts for this module, which is mounted next to the engine ecu under the glove box, comes from a fuse under the hood, when i pulled that fuse it disintegrated into powder, fairfax county road salt destroyed the fuse. replaced it, no more shifting issues. car now has 300k on it still going.
that computer, in my case, had a RESTRICTIVE FLOW 12 volts and passed a 12 volt meter test but failed under load to due a decrepit fuse under the hood
I plugged a new power source control ECU in from a junkyard car and my prius started up. But, after sitting overnight, failed to start the next day. What could cause it to start once and then not after sitting? Another junkyard psc mpx unit does not power on the car but when swapped in a prius that will turn on does work. Though my original one does not work so something broke mine. The IG1 relay was getting 12.5 volts but it was acting a little weird during the testing of it. My probe needed to be in a certain spot to get any voltage.
Since earlier this year, I've been having trouble. First, it appeared the smart key ECU wasn't acknowledging the key. Replaced that EU and reprogrammed keys. It worked intermittently. The key has always been able to lock/unlock doors even if it couldn't start the car. Then, it would only turn on if I refreshed all ECU via health check several times. Now, it won't work/turn on at all. Except the one time I replaced the psc mpx ECU.
No but I just replaced it in January and it powers everything else - headlights can turn on, turn signal, etc. Through tech stream I can even roll the power windows down.
Can you post a screenshot of the latest techstream health check results? You mention pulling codes from some ecu's or commanding windows up & down with Techstream- that requires some communication. Then you have recent posts about not having any communication with anything. Just trying to understanding the status right now. (Might help if you keep all updates in one thread instead of starting new ones- that's assuming everything is about one car). Posted via the PriusChat mobile app.
WOW. What great information. This is Similar to the fuse box issues in a P38A Range Rover. The Fuse box is located in the engine bay and the temps get wicked hot and wicked cool. The PCB inside the fuse box plastic housing cant handled the expansion and contraction after about 7 years. This causes HUGE amounts of chasing your tail trouble shooting the ECUs and the BECM module communications. Symptoms vary with the weather as temperature change causes expansion of PCB and hairline fractures occur in the electrical paths on the PCB leading to weird electrical behaviors. The solution is to buy a new $268 fuse box every 7 years and just replace it. I spent hours until I replaced mine. Best money I ever spent.
Here is another just GENERAL thingy I learned over the years with respect to powering some of these computers, I had an f350 and the tranny went out, it was throwing you in the backseat when it shifted, the dealer guy on the phone said, check the dome light, and I was like, this guy is an nice person, well the dome was out, I later found LOTS of car makers use such tactics when powering some weird computer like a POWER TRAIN CONTROL MODULE to make diagnosis fast and easy. No dome power no computer power, goes into fail safe, throws you in the backseat. lol i didnt type "this guy is an nice person" it was change somehow, and thats funny, I said he was something else