2002 prius DTC trouble code help

Okay, the first thing I have to ask is if you have the OEM Cats or Aftermarket?

In the aftermarket case, the vacuum line that went to the HCAC unit on the OEM cats was probably plugged.

The ECU senses (P1437) that there is no vacuum variance in the vacuum and thinks that the line is plugged or the HCAC has failed. You need to install a vacuum pot in the vacuum line with enough volume to imitate the action of the HCAC. A small cruise control vacuum pot can do that job.
I use a Honda 1500 Goldwing pot.

In the case that you have the OEM cats with the HCAC, the sensor (p1437) is sensing no variation in the closed position of the vacuum circuit.
Either the line is plugged or the HCAC valve has failed or rusted in the closed position.
P1436 is sensed when the line is opened (vacuum leak).

The other codes are for lower than spec HV Battery signal, Block 3 is out of balance, injector #4 is receiving low pressure readings, and the VSS speed sensor has out of spec readings.

One thing that all of these has in common is that their ECUs are directly effected by the 12v battery, especially in start up booting of the system. A minimum of 12.2 volts is require to start up and boot the system. Less than that will cause inefficient/incomplete boot up of the system.

First thing I would check is the condition of the 12v battery.
1 day, 2 weeks, or 2 years old, even new batteries can fail and a proper load test should be done to determine battery health. Have the battery completely recharged. Disconnect the 12v battery and pull the HV Battery safety plug and leave for several minutes.

When you reconnect all of the ECUs will be rebooted and reset.

Then run the car and see if any codes come up.
If any codes come up after this reset, they are probably more accurate than the codes you have now.

If the p3*** codes come up, I am more likely to believe that they are connection related, as opposed to parts related, and that you should check the terminals and buss bars for corrosion or loose fittings, especially on the modules in Block 3.

The "signal" terminology in the readings are commonly caused by the voltage and temperature sensor terminals and wires going to the ECUs and less as common to be in actual cell voltages in the modules, but if the connector and wires diagnosis does not turn up a problem, then there might be some component failures happening.

In the case of fuel injector readings, I recommend using injector cleaner before diving into replacement parts.

First step is easy, charge and test the 12v battery, and reboot, reset, the system.

Then take common sense steps from there.

 

Codes logged by the Engine Control Module:

P0500: the ECM didn't receive Vehicle Speed Sensor pulses while the car was being driven (2 troubleshooting pages)
P1437: vacuum is abnormal in the HCAC actuator line (5 troubleshooting pages)

In my 2001 repair manual, P1436 (which you don't have) is described as the one where the HCAC actuator seems not to move normally, and P1437 (which you do have) is described as the vacuum value not being held when the engine load goes above 30%, as you might expect in the case of a leak. This might be vice versa of the information Bruce has.

The Vehicle Speed Sensor signal has kind of a funny story in a Prius. In olden days, it would be generated right in the transmission, four pulses per driveshaft revolution. In your Prius, it is generated by the brake ECU (which has access to the four wheel speed sensors), from which a wire brings it to the combination meter, which serves as a signal repeater. The repeated pulse signal comes out of the combination meter (blue wire, C10 pin 13), goes to a junction connector where it emerges as a violet-with-white-stripe wire, then to another junction connector (J27/J28) where it forks into a bunch of violet/white wires going to the various things in the car that would like to have a speed signal.

My 2001 wiring diagram just lumps together all of the J27 and J28 terminals that carry the speed signal, and calls them all terminal G. So there'll be four or five violet-white wires there. At least it does show that the one to the ECM is one of the two connected to J28. The one from the combo meter will be one of the two or three connected to J27.

Codes logged by the HV ECU:

P3000-123: "Hey, did you notice the battery ECU has codes?" (see the P3013 below)
P3109: the HV ECU is not communicating successfully with the brake ECU (2 troubleshooting pages)

Codes logged by the battery ECU:

P3013: the third block of battery modules has internal resistance out of spec (3 troubleshooting pages)

My 2001 manual doesn't associate any of the codes you have with injectors at all.

The claim that a "minimum of 12.2 volts is require to start up and boot the system" does not appear in the repair manual, and also does not match my experience. Like the later generations, the manual does contain notes (see, for example, page DI-8) to charge or replace the battery before proceeding with diagnosis if the voltage is below 11. It does not say 12.2, which is well within the voltage range that nominal "12 volt" electronics are built for.

There are some trouble codes you can get from some ECUs (for example, C1241 from the brake ECU, C1551 from the steering ECU) if the voltage goes below 9. Logging those DTCs would be correct behavior of those ECUs, simply reporting the low voltage for you to know about. In my experience, the ECUs don't show issues with booting up or correct execution until still a couple volts below that.

 

I'm sorry that somebody thinks that a couple of points I have made are false.

I double checked. P1437 is vacuum plugged or closed. P1436 Is vacuum opened or leaking.
This vacuum issue may be closely related to the P0500 code, as the VSS switch is in the same vacuum circuit.

The rest of the codes are commonly related to the ECUs receipt of information, and not necessarily that of the HV Battery's condition, though it could be. My preferred method is to diagnose for the simpler and less expensive troubles before I move on to the bigger ones.

Yes, the car can boot up and start with as low as 11 volts in the 12 volt battery, and No, unless the battery is over 12 volts, preferably 12.2+ volts, the boot up of the ECUs and the overall system may not be efficient enough to guarantee the proper boot up conditions, and false or unreliable trouble codes can abound. This actually is a simple and practical fact of computer-based systems of many sorts, automotive, or otherwise. (Will my laptop boot up and operate on 12v rather than the 15v it is designed for? Sure, it will. But is there a potential for problems caused by low and improper boot up voltage? There certainly is!)

This comes from 40+ years of electrical/electronic motor vehicle diagnosis and repair experience (cars, motorcycles, snowmobiles and commercial aircraft). It is not totally based on the information from some sort of manual.

I do closely use service manuals but find that long term experience in successful and productive work sometimes supersedes a manual. A healthy balance works best.

 

While I won't reject the idea that "experience in successful and productive work sometimes supersedes a manual", there still is some value, when you're going to say "I double checked" something, in disclosing where you checked.

I disclosed where I checked. That makes it possible for somebody else to check on me. I encourage that. Can you recall the source that gave you those meanings for P1436 and P1437?

What are you thinking of when you say "VSS"? The Prius Vehicle Speed Signal is electronically generated inside the brake ECU. sent to the combination meter, and redistributed from there. It is unrelated to any vacuum circuit.

That certainly could be said of the P3109 (HV ECU not communicating with brake ECU) and, in a different sense, the P3000-123 (the HV ECU is communicating with the battery ECU, and has received a message from it reporting a trouble code there).

You probably have succeeded in phrasing that carefully enough to avoid being shown up every time somebody successfully starts a Prius at under 12.2 volts. After all, you did only say may not be efficient enough to guarantee proper conditions, and false or unreliable codes can abound.

But if the bar to accepting a claim could be met just by wording it carefully enough to skitter away from disproof, we'd end up believing a lot of weird stuff. The person advancing a claim is usually expected to have at least some actual positive support to offer. Not just by alluding to "simple and practical facts" (that other people with relevant experience also know a thing or two about), but by, for example, showing some cases where "false" codes were in fact seen, and at what voltage, and exactly how those codes were judged to be "false".

That last condition is kind of important, because there are plenty of posts on PriusChat where people have used the "triflingly reduced voltage makes false codes" canard to support itself. ("No of course I didn't check out what the code means and whether it's false! Why would I do that with a false code?") And often, without looking up how narrow the conditions are for detecting the code in the first place, will feel it must have been false if, after doing something with the battery and clearing it, it hasn't come right back again.

Actual support for the "false" codes idea, not just circular reasoning, could be found in posts where someone did look up the code, find out what actual conditions that code indicates, and show that those conditions did not exist in the car when the code was set. Maybe someone else has better luck finding such posts than I do.

I'm sure we agree that the specific codes whose actual meaning is "hey, did you know the voltage is low here?" are not "false" codes, when they are telling you exactly what they mean, and even though they don't come back when the voltage isn't low anymore.

That's a fair question to ask, like this one is; will the microprocessors in the car's ECUs boot up and operate on the five volts they are designed for? They will and do, as long as the on-board VRMs that downregulate the car's nominal "12 volt" supply to the needed 5 are able to do their jobs. Without relying on some sort of manual, my experience is that such VRMs tend to keep their output well regulated until the supply gives less than a couple volts headroom above the output. That fits pretty well with my experience that the Prius ECUs really will start to get wonky as the supply nears seven volts or so (operating, not resting).

One nice consequence of that is that the voltage thresholds where the various ECUs log actual "hey, low voltage here" codes are comfortably above that (typically around 9 or 9.5). So the ECUs have no problem executing correctly to log those codes when appropriate, and if the supply voltage did get down to those thresholds, at least one of those ECUs is likely to have logged one of those codes.

So you don't have to rely solely on how you judge a multimeter reading of the battery at the time you start your diagnostic work. You can also take into account any voltage-related codes you find in the ECUs, telling you about what voltage may have dropped to in the recent past (often with the exact value saved in a freeze frame).

But of course that works best when you hold off on assuming codes are false until you've seen what they are.