Gen 1 2002 Prius P1636 Triangle won’t start

P1636 means that the main engine computer (ECM/engine control module) and the HV computer (HV ECU) are having a communication problem. ("When [ECM] communication with HV ECU is interrupted for 1.5 sec. or more").

So it's likely because one of those computers has a problem, or the wiring harness/connectors have a problem. My guess would be the latter. The HV ECU is inside of the battery case. I'd start by a simple visual inspection of the harness connector there. The ECM, I believe, can be accessed behind the glove box. I'd next do a visual inspection there.

You're not a mechanic and dad's not great with electronics. Does anyone at least own and know the basics using a digital voltmeter?

And just because corrosion was cleaned up in the HV battery case doesn't mean it is good. Does the elm read the HV battery data? If not, look up the Dr. Prius app. Or if you want to get ambitious, search here for getting a "mini-VCI" Techstream knockoff.

 

Hi!

Your story sounds maybe like you *might* have a ‘bad high voltage battery’ - that can usually be fixed quite easily. The high voltage battery is around 300 volts - and 50 volts can be fatal. So - caution is required around the high voltage battery.

The errors where one computer can’t speak to another - that is usually the 12 volt battery being low voltage / flat (some computers don’t boot up). It is in the boot of the car, in the left hand side. The 12 volt battery should be at least 12.5 volts when you check it when the car is ‘off’. You can use a normal car battery charger on that (because it is a normal car battery). It should be charged outdoors (the car outdoors or good ventilation if in a garage, or charge it during the day using a normal 12v car charger (buy the slightly more expensive ones with multi-stage charging).
- Today I took my Gen 1 Prius for the first government check since I owned it; most people take their cars to private garages - but this was an official testing station!!!!
—- I bought the car in December 2019.
—- in April 2021, The 12v battery was dead, I charged it up but it needs to be replaced. Today I got : ABS error, airbag error, battery error, hybrid system failure - all due to a partially dead 12 volt battery!! After charging the 12 volt battery (and disconnecting the battery for 30 seconds (30 seconds is fine, but try 5 minutes if the errors keep recurring).

Your story also sounds like the ‘inverter pump’ has failed. This makes the inverter slowly overheat - and this causes problems, including the 12 volt battery going flat (the inverter ‘inverts’ a 12 volt supply to charge the ‘12 volt normal car battery) - the inverter can shut off if it is overheating.

 

OK I read you have a new 12v battery - which is good!

A basic multimeter will allow you to check the 12v battery voltage; it should be at least 12.0 volts, and between 13.7 and 14.5 volts when the car is powered up.

you need to check the inverter coolant pump - it is easy (YouTube link in next post);

Your ‘high voltage’ battery can still be faulty - even if cells were changed - that probably is one problem with your car - which can be fixed, after simple testing using a basic multimeter.

 

If you don’t have water flowing with the test in this video, you must fix that before any further tests!

 

Sorry, I must not have seen this at the time, and it may have sent you in the wrong direction.

The ECU that's inside the battery case is the battery ECU. The HV ECU in a Gen 1 is beneath the carpet under the front passenger's feet.

If P1636 is still the trouble code you've got, there is still electrical troubleshooting you need to do between this ECU and the ECM (which is behind the glove box). Progress may depend on solving that problem.