After a deer committed hari-kari last October taking out our 2005 Prius I located a suitable 2009 with a thrown rod and moved the engine from the 2005 into it, once I dug the engine out of the firewall. I re-used the 2009 inverter module and all 2009 engine sensors and TB, since the 2005 TB was smashed beyond recognition. . Since then though I have not been able to get the readiness monitors to stay reset even with a new 12volt battery and a type 27 later jumpered in also, "just in case". No, I do not have Techstream but I don't think this is a situation where Techstream would help anyhow. Since everything would complete the readiness cycle but the EVAP I've been concentrating on that until this morning when I realized that the EVAP takes, I believe, a couple of power on cycles to clear. At that point I realized that the ECM must not be maintaining it's memory. (Duhh) I've checked all fuses including the one on the 12v batt and am lost at this point. Anyone have any suggestions, I sure could use it. (FYI, I've been working on cars for over 60 years and professionally am an industrial electrician/programmer and troubleshooter. It shames me that this has me stumped...)
Why? Techstream would let you look at all the things being monitored and see which isn't working. See the 2nd post in this thread: Monitor not ready - catalyst evap system o2 sensor | PriusChat Other capable OBD2 analysis systems can do the same things (the ones that cost a couple of hundred dollars, minimum). Maybe the Autel AP200 could as well, and it is relatively inexpensive, but not as inexpensive as a miniVCI cable and Techstream of dubious provenance. If I had to guess a simple explanation it would be that you left something unplugged (easy to do in an engine swap, especially a ground cable since there is no empty socket to show the problem, just an empty bolt hole), or maybe one of the connectors was dirty and there is a faulty connection. Also, you know the 2009 had a blown engine, do you know that it was working fully before that happened? One of the devices being monitored may be broken. Is there a CEL? If so, read the codes, preferably with something better than a generic OBD2 reader, which will not be able to access everything.
For some of the ECUs in the car, the voltages of the incoming power supply connections are among the PIDs that Techstream or another scan tool can query the ECU for and show you. I don't remember for sure if the ECM is one of the ECUs that can do that, but it's worth a look. If you can connect to the ECM with the car on and it shows you a reasonable 13ish voltage on a circuit with a name like IG (which is on when the car is on), but not on a circuit with a name like B (which is supposed to be powered all the time and maintain the unit's memory), then that would confirm that a person should look for where there might be an open in the wiring bringing power to that B terminal. Without power there, the ECM is going to forget everything it learned every time the car's turned off.
=============== Why do I suspect that TechStream would not show the memory retention voltage? No good reason, I just doubt it and as I said, it's a mute point since I don't have TechStream anyhow. The ECM is off when the retention power is needed and I just don't think they bothered to sense it's level when it's on, but a lot of CPU's do just that so I could be wrong. I did drive the donor car with the thrown rod and three sides of the crankcase knocked out, so no oil, and the emission readiness monitor was cleared on it. (We strap towed it 70 miles home at below 35mph but I tried to keep the engine from starting, regardless, it was already ruined... I had a lot of time to look at things while being towed.) . I also ran the totaled car on propane, since the TB was smashed out, once I cleared the air conditioner 3-phase fault from the wires being cut. It ran and moved under electric power and looked good even if a little loud. Today I pulled all of the connectors behind the glove box and inspected the cables and socket pins. I did pull the harness out for the engine swap so there is a possibility that I damaged the harness. I also kept the engine harness from the wreck so I have a spare if it's comparable.. Tomorrow I'm going to crawl through the schematics and find the memory retention input to the ECM and probe it. Wish me luck.
======== Today I tested it and after being powered off for 10 seconds all readiness monitors reset, so it seems reasonable that this is the problem. We've put over a 1000 miles on it trying to correct this (and another self inflicted fault) and the car is running good in all respects and getting good mileage. Time to crawl though the schematics and find the fault... Thanks for the feedback.
Here's some reference. ETCS fuse supplies batt - B+ to ECM connector E7 - pin 4 (black), while EFI-1 fuse supplies batt - B+ to pin 6 (red).
Here's an example of a freeze frame from a gen 2 brake ECU showing that it monitors voltages IG1, IG2, BS1, BS2, VM1, VM2, +B1, and +B2: Granted, that's the brake ECU, not the ECM, I just didn't as readily find a screenshot for what the ECM monitors. But as you can see from the example, maybe you shouldn't bet against Toyota monitoring the memory-retention voltages (+B1 and +B2 here). The brake ECU has so many voltage readings because in gen 2 it's built in redundant style, two complete systems ("system 1" and "system 2", the names weren't very creative), with their own +B and IG power circuits, and also a big capacitor box in back supplying backup power if the regular 12-volt supplies fail.
