1602 and 3002 codes

You're in luck!

Good Prius Friend Hobbit hangs in that neck of the woods and I understand he has the NHW11 compatible, Autoenginuity scanner. Send him a PM and you'll be in excellent hands.

Bob Wilson

 

There should be a code for that issue stored in memory.

It's supposed to do that.

There is no code that indicates that the sensor needs to be replaced, only a code that indicates that something is wrong with the circuit. The actual issue needs to be pinpointed before parts are replaced.

He may be right. Some aftermarket scanners (the Launch X431 comes to mind) can cause this effect.

Such scanners often falsely report codes, so it's hard to know where you really are until you get a report from a scanner that can be trusted. The Autoenginuity scanner has been mentioned. Unfortunately, that scanner has a checkered past with the Gen 1 Prius, in terms of connectivity as well as accuracy. There is ample evidence of this in the archives.

Versions prior to 8.2 can falsely report nonexistent codes, and cannot communicate with some key modules. Version 8.2 has apparently addressed some communication issues, but its accuracy remains unknown.

A few folks have reported experimenting with one, but have not, as far as I know, tested it enough to determine whether or not the issue with false codes was fixed.

I would recommend finding someone who can record codes and subcodes as well as enhanced freeze frames, and have them record all information prior to clearing codes, and then give that information to you, as well as information on any codes that return. Since your vehicle appears to have multiple codes, I would recommend a factory level scanner or equivalent.

Folks on this forum may howl at such a suggestion, but it's kind of pointless to try to diagnose a vehicle without knowing the validity of the information that you are using to diagnose it.

 

I was a complete *idiot* today and forgot probably the most
important piece of gear when packing up for this meeting --
the laptop with AE and the obd-ii widget! But given the type
of problems, all seemingly having to do with communication
between ECUs, I wanted to unearth the hybrid ECU and have a
look at its connections. In the Classic, it's buried under
the slanted part of the passenger footwell. Wiring looked
okay physically, reseated the connectors on it and the engine
ECU behind the glovebox. Then I got a scope on the various HTE
and ETH and HTD and such serial-comm leads and they all look
solid, passing lots of little data packets back and forth.
There's no CAN bus in this car, it's all dedicated RS485-like
differential pairs run between the modules.
.
We also checked the throttle body; nice and clean inside. And
the 12V seems solid enough, despite the battery being a couple
of years old. But that's about all we could poke at sans scantool,
so we'll have another go at it in a few days. It's starting to
sound like the indy techs pulled the wrong codes, because really,
if there's a problem with the hybrid computer talking to the engine
computer the car will have a bit of difficulty actually going
anywhere.
.
_H*

 

We had another crack at this car today, with proper diagnostics.
The "ecu malfunction" code was still present, along with a more
generic P0171 "too lean" code. We already know the ECU comms
are fine, having seen healthy bits on the scope. We cleared the
MIL and started over, and the first thing I started watching was fuel
trims. Long-term was like 20% or more, and short-term all over the
place; both rose significantly as the engine was placed under load.
While the car *seems* to be running fine I did notice a slight
stumble when running the engine up to its 2400 RPM test condition
by pressing the go-pedal in Park, as well as a significant correction
in mixture trim and a resultant dip in RPM on going to Neutral to
come back off that to base idle.
.
So now it boils down to a typical lean-condition engine problem.
The supposed communication errors did not return, so I guess those
don't self-clear in this car without help.
.
Lean fuel-trim conditions that change like that between idle and
loaded often indicate a dirty MAF. I took a look at it and where
I should have seen those nice little white beads I saw dark brown,
so I tried my cleaning trick with alcohol. In contrast to the two
other MAFs I've cleaned this way, this one didn't really take to
it and the wire elements still looked dark and like they still
had gunk stuck to them or that they might have even been a little
burnt somehow. And the fuel-trims didn't change. I could drive
the long-term down temporarily by holding my fingers in the
throttle throat next to the MAF "pedestal", forcing more air
through the MAF itself.
.
Force-charging to create a higher engine load drove the long-term
trim up over +40%, around which the MIL went back on. *sigh* So
the current theory is that a new MAF is needed, and we can't rule
out the possibility of a vacuum leak somewhere in the maze of hoses
but that wasn't anything we were going to find in a quick later
afternoon of looking around. I wonder how it got that gunked-up
in the first place...
.
_H*

 

Excellent report:

PCV valve?


The small outlet hole at the 11:00 o'clock position relative to the MAF sensor might be the source?

Other than doing a compression leak-down test, I wonder if there is another way to detect excessive blow-by?

Are you having any problems with connecting the AE to the NHW11s? I've found setting it to ISO9141-2 seems to avoid inducing ABS errors. Better, I'm still seeing intermittent problems.

Bob Wilson

 

Well, once again "morning after" hindsight wins. We could probably
have swapped in the MAF from *my* car that was sitting right
there behind us to test things and help localize the problem; I
think they're exactly the same unit in NHW11 and NHW20.
.
Both PCV hoses come in safely underneath where the MAF is
located, so I don't think the perennial "oil fog" problem that
goes on down there can affect it. I've never seen oil on any
of the MAF parts, just a little bit of light dusty stuff. But
the wires in George's unit almost looked burnt somehow.
It was *sort of* working as holding a finger over the tongue
or next to it did affect engine idle and the LTFT, but I don't
think it was reading right.
.
_H*

 

See my post #12, looks like the MAF is different although the throttle body assembly is the same.

 

What sort of prices for a MAF sensor?

Bob Wilson

 

Did you try spraying carb and choke cleaner around the inlet side of the engine to see if you have a air leak, what sort of readings were u getting from the o2 sensors.

 

The MAF sensor is priced at $165 MSRP and you can buy it for $125 here:
http://www.trademotion.com/partloca...rius&year=2001&catalogid=2&displayCatalogid=0

http://www.trademotion.com/partloca...rius&year=2004&catalogid=2&displayCatalogid=0

Looks like Classic and G2 have different part numbers.

 

Why not use the scan tool to identify the problem?

 

It is fairly common in the NHW11 to clean the throttle plate area of 'gunk' to avoid 'sticky throttle' and the MAF is on the far side of the throttle plate. I'm beginning to wonder if there might have been a design change between the NHW11 and NHW20 that reduced the amount of fuel and oil-mist laden charge that drifts back to the throttle plate and MAF area?

The ZVW30 engine has a space in the block to separate out the oil and air. But I was wondering if the NHW20 might have a slightly longer section between the throttle plate / MAF area and the manifold. Perhaps a spacer or longer throttle body?

Perhaps an IR camera might be able to observe a fuel and oil-mist vapor rising up to the throttle plate area?

Bob Wilson

 

P0110 and P0100 codes can be set if someone disconnects the MAF sensor when its circuit is energized.