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hello

after getting the dreaded DTC 17125, i got a new TC in last week

engine got out for this operation
while the engine was out, i asked the mechanic to gut the precat
car is stock now but will get MTM remap in january

got the car back on friday and ever since it's a christmas tree on my dash, got lots of DTC that of course never got before the TC replacement

erased them several times but they always come back

i've got DTC for the 2 lambdas before cat if i'm correct
16515 - Oxygen (Lambda) Sensor B1 S1: Signal too Low
P0131 - 002 - Lower Limit Exceeded - MIL ON
16534 - Oxygen (Lambda) Sensor B2 S1: Malfunction in Circuit
P0150 - 008 - Implausible Signal

and i've got a lot of misfires detected
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - Upper Limit Exceeded
16688 - Cylinder 4: Misfire Detected
P0304 - 001 - Upper Limit Exceeded
16687 - Cylinder 3: Misfire Detected
P0303 - 001 - Upper Limit Exceeded
17536 - Fuel Trim; Bank 1 (Mult): System too Lean
P1128 - 001 - Upper Limit Exceeded - Intermittent

tested the MAF (see attached file) and they look OK, even if i think there is a big difference between both banks, sometimes up to 30g/s at WOT
took out the airbox and put it back again, to check if it were installed correctly

so now,
-are my MAF Ok? because i'm going to replace them and the rubber seals as well
-can the gutted pre cat causes the lambdas related DTC and/or the lean related DTC?
to sum up, WTF is going on with my car?

Sounds like the B1 and B2 lamba sensors have been mixed up when the engine went back in.

I'm guessing it has nothing to do with your mods.

MAF values look fine.

You need to log the lambda correction.

The misfires are probably from the incorrect mixture caused by the fault in the lambda circuit.

Look at the fault codes again, it looks like there's a problem with the wiring. You need to check:

1. The probes go to the right connectors (although they should be colour coded unless the probes have been replaced at some time in the past).
2. There is no damage to the wiring (easy to pinch / crush a wire when manoeuvering the engine into place
3. No damage to the connectors.
4. Check the resistance of the heating element if you have a multimeter. Measure between the first 2 pins (there is a group of 3 pins then 1 on it's own. The one on it's own is n° 4). Resistance should be 8 ohms +/- 4.

so MAF are ok then, good, that saves me some money

will log the lambda now

so you think they mixed up left and right lambda when they put back the engine and cats?
that's plausible as they took out the lambdas before cats to gut the precat

i just checked the connectors postions
from left to right, it's green, brown, and black
and there is no mix up, green on green, brown on brown and black on black, looks like everything is correctly connected

green and brown are the post cat lambdas, right?
where is connected the second pre cat lambda?

The lambdas might be plugged into the right connectors, but are they in the correct position on the manifold? Could be banks 1 and 2 have been swapped. The effect would be the same as mixing up the connectors.

Green and brown are after the cats.

Bank 1 probe one is black.

Bank 2 probe one is on the other side of the engine bay, just to the left of the EGT connectors.

some news

checked the resistance of the lambdas, they all look fine, within tolerances, 9-10 ohms for all 4

btw, it was a PITA to get to the right black one, had to took out the airbox

what if i swap position of the black connectors lambdas? (if cable length permits it)
lambda connected to the left connector (when facing engine) goes to the right connector and vise versa
dumb idea?

or should i log before?

The connector on the left goes to the left lambda and vice versa. Difficult to see where they go once the get down behind the engine. It'll be difficult to swap the connectors. If you're handy with the electrics you could rig up an extension temporarily to test with.

If you do log, clear the ECU DTCs first to reset the lamda correction to zero.

i managed to swap connectors

after reset, i'll go for a test ride and log

Might be interesting to put them back to how they were and do a log that way as well.

good news

DTCs gone, it was the mix up between the lambdas before cat that causes my problems

drove 150km today and everything is fine
now i have DTCs related to the precat gutted (cat Efficiency Below Threshold bank 1 and 2) don't care about them

thanks Shoppinit for the help

Yay! Good result

Make sure that you tell MTM to map out the offending lambda sensors.

You really are the man, Shop!!

Wow. Very impressive Mr Shop

Great fault finding Shop !