C1343 error code with Techstream

The C1343 with info code 571 refers, as it says, to a problem achieving the target brake pressure in the right-rear brake line.

You can see in the freeze-frame data that at that instant, the target fluid pressures in megapascals were: 3.1 for the front left and right, and 2.8 for the rear left and right.

The actual measured pressures for those four lines aren't shown in megapascals, but just the raw volts coming back from the pressure sensors: 1.13 front right, 1.11 front left, 0.64 rear right, 1.05 rear left.

There are eight pages of workup for this code in the repair manual. On the seventh page there's a chart for the pressure sensor voltages to actual pressures in megapascals. The readings should be 0.65 to 0.75 V at around 1 MPa, and around 1.05 to 1.2 V at around 3 MPa.

As the actuator was trying for 2.8 MPa (call it 3) at both rear brakes, the 1.05 V reading from the rear left seems right in the ballpark, but the 0.64 V reading from rear right is way low.

So ... the steps in the eight workup pages start with the obvious: is there a leak in the RR line? If not, the checks go on: is that low sensor voltage because the sensor is right and the pressure is low, or is the pressure actually correct but the sensor wrong? That can be checked by plumbing a brake pressure (or "LSPV") gauge into the line, and comparing its reading to what the sensor is showing. Or is the pressure ok and the sensor ok, but the wiring from the sensor to the ECU flaky? Or is there a bit of grot stuck in one of the valves in the actuator so the pressure isn't being held, but leaking back to the reservoir? Or is the ECU itself on the fritz?

They also have a test for whether the pressure reading isn't steady because the rotor is warped, but (a) I haven't heard of that happening to drum brakes much, and (b) your freeze frame shows all four wheel speeds were zero at that moment, so I'm guessing that's not it.

B1421 is a low signal from the solar sensor on the dash. You'll always have that code if there isn't strong sun beating down at the moment you read the codes.

B1271 suggests there was a communication glitch between the combination meter in the dash and the gateway ECU at one point. Have you noticed any issues with your combination meter? Could have been a one-off; does that code come back if cleared?

 

If you take the information you've got to the local mechanic, and make sure they have access to the Toyota repair manual (or some alternative that is actually comprehensive!) it ought to be possible to figure this out. The problem could turn out to be in the actuator; I can't promise it won't. One checks the easy things first, and follows the evidence.

I wouldn't be distracted about the battery at this point. Your freeze frame shows the brake code was logged when the incoming supply voltages were between 13.02 and 14.11, so clearly when the car was in READY, and nothing looks wrong about that.

Maybe the B1271 is remembered from when you had the combo meter issue?

 

Here is the workup for DTCs C1341, C1342, C1343, C1344 (all with various INFs, or detailed codes)

https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/21avn/cic13416.pdf

 

Stupid question here... but I want to confirm... when it says RR, that means passenger side rear?

 

Yes.

 

In countries where the driver sits on the left.

 

^ +1^

Lefts and rights in a car are always in reference to sitting in the driver's seat looking forwards.

The fact that there are LHD and RHD vehicles makes the driver's side/passenger's side (same with the UK's near side/off-side) references ambiguous unless they are qualified or the location of the car is known. (Even then that can not necessarily be relied upon, as a European car in the UK will be LHD whereas the UK is a RHD country (and vice versa)).

 

What was the real problem on your car bud

 

What makes you think the C1343 was not 'real'?

 

Presumably, they checked for any sign of leaking brake fluid and found none. They should have then bled the air out of the front and rear systems and again the assumption is they did that and found no air in the line. Next, they should have cleared the codes and checked to see if the DTC reappeared – the assumption it did reappear. The next few steps are more involved and time-consuming involving checking two more things, 1) The harness and connectors between the skid control ECU and the brake actuator assembly. If there is no fault found here then the next step, 2) is to check the pressure sensor by checking its readings against actual. If that checks out then the next step is to check the brake disc and pads for vibration. This would only be done if freeze frame data or customer problem analysis indicated it as a likely avenue to pursue. Given your code points to the RR circuit, it probably was skipped, and that only leaves replacement of the brake actuator assembly as the conclusion.

As long as you are confident the complete diagnostic was completed, then the dealer's advice is reasonable.

 

Obiejon12. Did you finally fix it? Did you have to replace the ABS actuator? I have the same issue right now…

 

Your profile says you have a Gen 3 so you should post (or look for posts) in the Gen 3 forums. This is one area where the Gen 2 and Gen 3 are different, so you want good information to avoid chasing tails or going down rabbit holes.

 

Apologies for not clarifying.... this is for a friend's Gen 2.