Gas engine does not start

I don't understand why SMR would come up, as that has nothing to do with any of the potential troubleshooting tips for P3125.

Failsafes come under: normal driving, limited driving, or no driving. Speculation: it is possible that the HV ECU detects an error condition related to MG1, thereby preventing engine start, but allows limited driving using power from MG2.

 

I recently purchased a 2002 with code p3125 and info code 366 (i think I will have to check my notes on the info code) Mine turned out to be the inverter. One thing to check would be is the inverter coolant pump running? It should run any time the key is on . The HV ecu is supposed to be on the floor in front of the passengers feet under the carpet and a metal plate. The test for my info code was to check the harness from the HV ecu to the inverter. That may be why this was apart. However mine the ICE would start but the 12v and the HV batteries would not charge. I also have seen some times the throttle motor will lose its idle setting and keep the throttle plate closed the ICE will not start. To overcome this you can open the air filter box and with the vechicle ready off you can manually open the throttle plate and stick a small screw driver down there to keep it open a little just the width of the screw driver blade. Ready on the car and it should start. Let it run for a min or so the remove the screw driver and it should idle on its own. You may need to disconnect the 12v battery to clear the codes and sort of start over before doing this. I am just sort of guessing here without the info code. But it can't hurt to try.

 

Have you ever seen this on a Gen II? One of regulars here posted a few months ago about having P3191, initially caused by carbon buildup in the throttle plate/bore, but ultimately fixed by ECM reflash per TSB for 2004. That story has always puzzled me. The TSB reprogramming only makes the engine crank a few seconds longer, whereas losing the learned value of the TPS makes more sense.

 

Can you get your hands on another inverter? Even if it turns out not to be the problem, you'll have a spare, since these are known to have issues.

 

I know what TSB you are talking about. Part of that TSB is to remove the EFI fuse to rest Idle values after the throttle body is cleaned. This is sort of the same but I have never seen the gen II actually not start untill the throttle plate is opened. Only the GEN I.

 

If you disconnect the 12v or clear the codes. Will it try to crank or does it set the code right away? I dont think the problem is in the transaxle. Most likely the inverter or harness issue. Does the inverter coolant pump run? If you can get the info code I can get the diagnostic info.

 

Ok I have been trying to figure out what happens in fail safe mode. All I can find is that when p3125 is set with a certain info code (there are about 50 info codes for p3125) it will go into limited driving fail safe mode. This mode should not cause MG1 not to crank the engine. Looking at my hybrid diagnisis text book there is a side note that says:
A vechicle which has set both p3120 and p3125 may be difficult to diagnose. The reason both codes may set is because two independent current sensors are evaluating inverter and motor generator performance. If a tire slips or a motor-generator mechanically binds or fails current flow values will be high. The inverter current sensor may detect the high current first and assume that the high current flow is caused by the inverter instead of the motor generator.
Diagnostic Procedure
In most transaxle cases the engine will not start or makes a strange whining sound when cranking. If MG1 operates, swap the HV ECU. If the code resets , replace the inverter

If MG1 does not crank the engine, replace the inverter first

Sounds like the inverter needs to be replaced. I have the old one from my car that would start the engine but it would not charge the batteries. I would give it to you but it might no be worth the shipping cost.
Hope this helps.

 

You talking about this safety switch, I had this issue with my last honda. I parked and never started until 5th mechanic opened the glove box, pressed the magic rubber button and the car started like new. He called it pressure switch or something like that. He showed me that even when you rapidly hit the dash then the switch is activated. Great for anti-theft device. I don't know where is this button located in Prius... Maybe worth trying... Please accept apologies for spoiling the thread.

 

Fred, that's a wonderful job tracking that down! You've really had your work cut out for you on this car.