P1636 and P3002 - Prius 1st Gen.

This may be a little tricky because I need a URL to identify an image and these are attachments to another post. Let's get started:

• P1636 - When communications with HV ECU is interupted for 1.5 seconds or more. Ambiguity group:
  • Wire harness
  • HV ECU
  • ECM (Engine Control Module)
• Signals HTE+ and HTE-, a private communications link, two wires between the HV ECU and engine ECU
  • Volume one shows the engine ECU removed with the third connector exposed to access HTE+ and HTE-. Turn the car to IGNITION and measure between HTE- and HTE+. Look for a digital pattern coming from the engine ECU (i.e. called beacon signal, +/- 2 V peak-to-peak.) No signal, the engine ECU is bad, replace it.

Although not required, I am surprised there was no code in the "Hybrid Control" or HV ECU. Yet the Techstream did not identify it as failed.

• P3002 - When serial signals transmitted from HV ECU. Ambiguity group:
  • Communication bus line
  • HV ECU
• Signals HDT+ and HDT-, a private communications link, two wires between the EV ECU and battery ECU.
  • The recommend disconnecting the connectors and ohm out the two lines. If the wire harness is OK, they recommend disabling all other electrical loads, clear the codes (disconnect the 12V ground for a minute or so) and retest. I car returns the code replace the HV ECU. Otherwise, stepwise re-add the loads to identify the problem source.

So looking at the antilock brake ECU, we find:

• C1213 - When the ignition switch is ON, abornmal communications with HV ECU continues for 0.5 sec or more
  • HVI+ or HVI - circuit
  • HVO+ or HVO- circuit
  • HV ECU
• Signals HVI+, HVI- and HVO+ and HVO-, two private communications wire pairs
  • Ohm out the signals. If wires are OK, replace either HV ECU or brake ECU.

Notice all three codes include the HV ECU so this becomes a part of great interest. So the formal process is to test the engine ECU signals. However, it might be faster to bring up the HV ECU status on the Techstream to see if it 'working'. The HV ECU reads the shifter position. So while looking at the EV ECU, switch shifter position and verify the HV ECU is reporting the different positions. This does not give the EV ECU a clean bill but ensures we are seeing at least part of the HV ECU is working.

But it would be nearly as fast to access the HV ECU; remove each connector to look for visible damage, and; reseat connectors and test. Reseating connectors very seldom works until it does. But you want to see if perhaps some liquid might have gotten to the HV ECU and connectors.


Apparently the car was running (i.e., coolant hot) when the original fault occurred. Kind of a hot day, 97F.


The battery ECU looks excellent and you still have plenty of charge on the traction battery. All of the modules look good and temperatures are moderate (time of running Techstream.) Also, the 12.656 V means the AUX battery is looking good.

The common ambiguity group element is the HV ECU. So I was start looking hard at the that one and consider swapping with another. HOWEVER, I understand there is a 30 minute ON state required so the immobilizer will let the car start.

Does this help?

Bob Wilson

 

You did fine. I just needed a URL to the attachment and my browser using a CNTL+click generated one based upon the stored image location. Many past systems had a limit on how many images could be uploaded because it cost disk space. So in the past we would get a URL to a server holding the files and this put no load on the server BUT if the remote image server went away, so too the photos. So it is a tradeoff.

Intermittent problems are the hardest ones to isolate. It is very hard to know if anything actually had an effect.

New to me.

That is fine, 167F = 75C is perfectly fine. It means the car is capable of auto-stopping the engine.

The "rpm and engine speed showing zero" does not bother me as the car can turn off the engine at any speed under 42 mph. This is a normal, hybrid operational mode.

Because we lack full Techstream documentation for this car, I am loath to interpret the 'calibration' as embedding a date. We're humans who at a casino are capable of seeing patterns in random numbers. We really need something from Toyota.

Replacing the airbag harness could easily lead to this problem. It points at a different set of connectors that could be loose or have bent pin. Why was the air bag harness replaced? Was this car in a collision?

A wire can break within the insulation can be nearly impossible to detect by ordinary means. You have to 'catch' the problem when it occurs but using a VOM to ohm it out means pulling a connector and that alone can make or break a broken wire.

In the past, I would have the device on and 'giggle' the wire harness to try and induce the problem. However, given the extreme effects of an air bag deployment, this has significant risk! An air bag going off can kill and certainly injure anyone not 'in a seat.'

Dealing with intermittent problems:

• capture as many incidents as possible - a pattern may show up that looking at the electrical schematics and Volume 1 diagnostic manual may lead to a testable hypothesis. For example, do the signals identified pass through a wiring harness section near the replaced air bag harness.
• audit the last work - because this is the air bag system, there are special safety precautions that need to be followed. The air bag controller has its own, large capacitors capable of firing the air bags if the 12V battery supply fails in an accident. But it may be that the repair induced a broken wire OR the wire is broken somewhere else as a result of an accident . . . what cause the air bag harness to be replaced.
• investigate wires near any 'bent metal' - steel has a spring capability of being able to stretch and spring back to the original shape. But many wire harnesses are tied to steel body parts so their wires can be 'stretched' leading to a break inside the insulation . . . but the steel springs back holding the broken ends close enough to make a circuit . . . on some days.

Broken wires inside of insulation are a really difficult, intermittent problem. It is impractical to replace all of the harnesses. For example, vibration can lead to fatigue breaks inside of insulation and though the designers try to make sure the wires don't vibrate, there a cases where it is unavoidable. This can 'work harden' the wire(s) so a subsequent stress can cause a break inside the insulation.

That is my opinion so take it with a grain of salt. The collaborators here may have additional insights to share.

Bob Wilson

 

It's combined with the mass airflow sensor, they're a single assembly, right above the throttle body. It can well be warmer there than outside.

-Chap

 

Hummmm, wonder what caused it to fail? Critters? Spilt liquid?

If a condition does not reoccur, the third start will clear the check engine light. Meanwhile, the stored codes are retained. The best practice is to use the miniscanner to read the codes; save a copy and; clear them. That way you can begin to characterize how frequently the error condition(s) are occurring.

Bob Wilson

 

The codes are stored in memory much like the freeze frame data. If the problem comes back, the check engine light comes on again. It also resets the three-start counter.

In contrast, limp home mode is something else and impossible to ignore.

Bob Wilson

 

Have same issue 1636 -3002 and 3060
Did replacement of12v battery help?
Thanks
Don