Need assistance please

I think you need to figure out why you cannot retrieve the DTC. What scanners are you using, and have you tried Mini VCI?

If you cannot retrieve the DTC then you'll be reduced to guessing which is a bad place to be.

What is the prior service / accident history of that car and when was the last time that it ran without trouble lights on? For example if the car was flooded or struck by lightning then forget about trying to economically repair it.

The Classic Prius forum is a subgroup to the G2 Main forum.

 

That shop is lousy, if they are not using the correct equipment either.

Your scanner is essentially junk when it comes to a Toyota hybrid. It probably shuts down b/c it doesn't know how to handle the many ECUs and sub ECUs. Time to enter the 21st Century.

Get miniVCI and be done (Amazon, $25-$30). Doesn't matter which seller as they are all selling the same counterfit cable and hacked Techstream software 8.0+. Ideal to install onto a spare laptop running Windows 32bit Operating System. Many threads on install help available (32bit Win, 64bit Win, Mac), just search. Many here have been using miniVCI w/o issue.

 

You are deceiving yourself if you believe your generic OBD2 reader will read ALL Prius codes and sub codes with 100% accuracy. Many posts exist from people reporting false codes.

MiniVCI w/ Techstream gives you the SAME diagnostic capability as the dealer. MiniVCI is a counterfeit copy of the proprietary Mongoose cable ($495). Techstream is the software created by Toyota to read Toyota/Lexus/Scion (Daihatsu in Japan); One year software license use is $1395 and requires propietary cable. Reading codes at the dealer one time is usu $100+. Do you not have $25 and a spare junker laptop, or a friend in IT who will likely have access to obsolete laptops?

With miniVCI, you can properly and easily bleed your brakes; this is a $100+ value at your local dealership.

 

Since you own other Prius, you probably are aware that multiple ECUs are involved in managing the car's various systems: engine, hybrid vehicle, traction battery, steering, skid control, transmission control, body, immobilizer, etc. One of those ECUs may be causing a communications problem on the controller area bus that feeds the OBD-II port.

If you acquire Mini VCI and it also fails to read any DTC then at least you know you've exhausted all reasonable possibilities to read the DTC. However, you may find that it is successful where the generic code readers have failed. You won't know unless you try.

A generic code reader typically will be able to read DTC logged by the engine ECU. It may read DTC logged by the hybrid vehicle and traction battery ECUs. It probably will not read DTC logged by the other ECUs, especially the Uxxxx codes which will identify a communications problem. It probably will not read the hexadecimal DTC codes posted by 2G and newer Prius (where the letters A - F are used as well as the digits 0 - 9 for the last four characters of the DTC.)

An alternative, since you own another Classic Prius, is to swap over ECUs and see if you can get the problem to move over to the other Prius. Obviously that will entail substantial effort and may not result in a resolution of the problem.

Along the lines of using brute force effort, you should verify that every fuse is sound. Remove each fuse, one at a time, and use an ohmmeter to verify continuity. It obviously would not be helpful for an ECU not to receive power from a fused circuit, and that could be a reason for lack of communications on the CAN bus.

Also, clean the throttle plate and throttle body interior as that is a common reason for engine no-start. Make sure the mass air flow sensor is clean, use MAF cleaner spray if it is not. Remove the iridium spark plugs and inspect their condition as well as the physical condition of the spark igniters. Replace with the correct parts if needed.

Make sure the engine air filter is in good condition, replace if needed.

Make sure the 12V battery is fully-charged. Use a charger overnight, 4A setting, if there is any doubt.

A wiring harness problem also may cause the comm problem - for example, rodent infestation and resultant damage to the wiring.

 

That is definitely possible ... I don't think it's common, but certainly you are dealing with an electronic communication network and anything from shorts to opens to bad connections to nicked wires to EMI can interfere with the communication.

It's common enough that the sections in the repair manual that deal with pulling your codes also contain systematic troubleshooting procedures to pin down the cause of comm failures when you can't get the codes. You will probably want to follow those procedures, because there are a lot of possibilities and a procedure reminding you what to test next in an order that will get you somewhere will help a lot. I think a basic multimeter (and a grasp of what it's telling you) is all you need for most of the tests ... that, and some time budgeted for trim and/or carpet removal to get access to any of the connectors or wiring sections you might need to check.

-Chap

 

The symptoms are consistent with a severe load on the 12V battery system. Let's start with basics:

1. Make sure the 12V battery is installed with the positive towards the rear seat and the negative towards the rear bumper.
2. Measure the 12V battery voltage at terminals and share it.
3. Turn the ignition on to start and leave in running position.
4. Measure the 12V battery voltage at terminals and share it.

The cigarette lighter has a relay switch so it is not a trustable source. However, the OBD port has a fused, 12V pin that is always on:

Taking care to not short the pin 16, measure the 12V level with the key out and then turning the key on.

GOOD LUCK!
Bob Wilson

 

Pin 14 - this is the brake controller. The TechStream knows how to read the codes and values. However, a non-TechStream OBD reader, in particular the Scangauge, can spike the brake controller if it tries to sense the protocol. The fix is to disconnect this pin from any other OBD scanner so they won't spike it. Sometimes forcing ISO-9141 will work but don't trust auto-detect.

Pin 15 - this is ISO-9141 controller interface. It, ground, and B+ are all that are needed.

Now without the traction battery, the 12V DC-to-DC inverter, found on the bottom of the power inverter, might not try to come on. My hypothesis is the 12V DC-to-DC inverter might be FUBAR and clamping down the 12V circuit.

FYI, good news about the traction battery voltage levels.

Bob Wilson

 

If you still have the old inverter, the 12V DC-to-DC converter is in the bottom. Open it up and take a peek and post pictures. I think you'll be impressed.

The one I did had ICs blown off the board.

Bob Wilson

 

Thank you!

I've got another inverter whose 12V DC-to-DC inverter looks like a war zone. Hummm, wondering what in the inverter crowbar the 12V buss. Regardless, excellent job! Well Done!

Bob Wilson