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Persistent 997.1 C2S engine fault codes
- Thread starter MJK1
- Start date
Ok .. interesting .. my thoughts ..
I have a feeling the secondary air system is working just fine .. you can't really check it via the lambda readings on a warm up first start and be accurate but the trace on the lambdas does seem to indicate that this system is ok ... it may not be but i want to ignore it for the moment ..
The voltage is just wrong for both sensors pre cat .. these are not wide band sensors and even if they were its still the wrong voltage so im guessing the tester is just displaying it wrong .. it's also at minus 50 ?? just wrong !
If not then you Will have fault codes for both pre cat sensors as they are basically not working according to the voltage .
the switch up and down is fine so i'm guessing it is 0.2-0.8 volts but bank 2 is very slow .. that is indeed an issue.
Its also the sensor you have replaced .. and yet its still slow .. interesting .. its not the sensor but something else that's cause a rich / lean normal operation .. but too slow ...
Something restricting the exhaust gases that bank perhaps :?:
Post cat sensors .. again this tells a story ..
Bank 1 shows the cat is working ...
bank 2 shows the cat isnt working ..
The bank 2 sensor is switching rich/lean and i'm assuming this is on idle .. the cat is not doing its job and i suspect it might be damaged as well .. perhaps partially melted or indeed a knock at some point has broken bits off and parts have turned sideways thereby restricting air flow .
Your first point of call atm is to check the cat that side .. either a bore scope down the pre cat lambda sensor hole or just remove it and have a look .
That's my logic anyways and what i would be checking next on this rather interesting and difficult fault .
Quote from one of my previous replies .. seems like this was already an idea of mine lol
I have a feeling the secondary air system is working just fine .. you can't really check it via the lambda readings on a warm up first start and be accurate but the trace on the lambdas does seem to indicate that this system is ok ... it may not be but i want to ignore it for the moment ..
The voltage is just wrong for both sensors pre cat .. these are not wide band sensors and even if they were its still the wrong voltage so im guessing the tester is just displaying it wrong .. it's also at minus 50 ?? just wrong !
If not then you Will have fault codes for both pre cat sensors as they are basically not working according to the voltage .
the switch up and down is fine so i'm guessing it is 0.2-0.8 volts but bank 2 is very slow .. that is indeed an issue.
Its also the sensor you have replaced .. and yet its still slow .. interesting .. its not the sensor but something else that's cause a rich / lean normal operation .. but too slow ...
Something restricting the exhaust gases that bank perhaps :?:
Post cat sensors .. again this tells a story ..
Bank 1 shows the cat is working ...
bank 2 shows the cat isnt working ..
The bank 2 sensor is switching rich/lean and i'm assuming this is on idle .. the cat is not doing its job and i suspect it might be damaged as well .. perhaps partially melted or indeed a knock at some point has broken bits off and parts have turned sideways thereby restricting air flow .
Your first point of call atm is to check the cat that side .. either a bore scope down the pre cat lambda sensor hole or just remove it and have a look .
That's my logic anyways and what i would be checking next on this rather interesting and difficult fault .
Quote from one of my previous replies .. seems like this was already an idea of mine lol
deMort said:
Thanks for the feedback deMort, I'm going to swop the O2 sensors for each bank over and measure the voltages again and see if the voltages swop with the sensors or stay with the bank. The parts list shows both upstream and both downstream sensors are common parts.
Depending on these results, I've also got a spare set of catalytic converters that I can fit to see if that makes any difference. I'll report back with the results.
Depending on these results, I've also got a spare set of catalytic converters that I can fit to see if that makes any difference. I'll report back with the results.
On the off chance you have a temp gun then check the temps of both Cats at operating temperature .. a defective cat will be colder than a good one ...
Ie ..
If the catalyst has stopped working, the front temperature will be about the same as or higher than the rear temperature.
In a good catalytic converter, the rear of the converter will be 20+ degrees hotter than the front.
if you have a spare then remove the old one and have a look .. i think if its faulty it will be obvious but fitting another will prove it .
Ie ..
If the catalyst has stopped working, the front temperature will be about the same as or higher than the rear temperature.
In a good catalytic converter, the rear of the converter will be 20+ degrees hotter than the front.
if you have a spare then remove the old one and have a look .. i think if its faulty it will be obvious but fitting another will prove it .
This evening I swapped over the upstream and downstream O2 sensors. I then did a cold start and recorded the same parameters. As you can see below the results were practically identical. This confirms the O2 sensors are all working.
Next job is to swap the catalytic converters and see what difference that makes.
Next job is to swap the catalytic converters and see what difference that makes.
I think I may know what was causing the Bank 2 O2 sensor error codes (P0153 and P0154). The bank 2 sensors were plugged into the wrong connector!!!! They are colour coded black (upstream) and grey (downstream) but surprisingly not baulked so it's possible to plug the sensors in the wrong way around. It must have happened when I installed the engine and I didn't notice whenever I was changing sensors until today. The sensor voltages are now matching across the banks.
I'm still not convinced the secondary air is getting into the exhaust manifold as the voltage is high towards the end of the secondary air injection phase which indicates it's running rich as shown in the diagram below.
I'm going to run it for a while and see if any new codes are triggered.
I'm still not convinced the secondary air is getting into the exhaust manifold as the voltage is high towards the end of the secondary air injection phase which indicates it's running rich as shown in the diagram below.
I'm going to run it for a while and see if any new codes are triggered.
Attachments
I think i can safely say i would never have gotten that fault in a million years without seeing the car !!
Clear the codes .. drive it for a while and see what fault codes you are then left with and we will take it from there .
Your last picture is a test picture of what should happen .. i suspect that's when you drivelink this system and graph the lambda sensor and not what you will actually see from a start up .
My guess anyways .
Clear the codes .. drive it for a while and see what fault codes you are then left with and we will take it from there .
Your last picture is a test picture of what should happen .. i suspect that's when you drivelink this system and graph the lambda sensor and not what you will actually see from a start up .
My guess anyways .
Attachments
Thanks deMort, I've erased all the codes so will monitor it over the next few days and see if it springs any codes. Hopefully all the codes I was seeing were due to the upstream/downstream switch of the Bank 2 sensors.
I notice that once the engine has warmed up on a drive, when I come to a stop the secondary air pump starts up for about 10 seconds. I suspect this is the engine checking the secondary air system by looking for an O2 sensor voltage drop as the air is pumped into the exhaust manifold. I'm sure it will soon trigger an error code if it's not working.
I notice that once the engine has warmed up on a drive, when I come to a stop the secondary air pump starts up for about 10 seconds. I suspect this is the engine checking the secondary air system by looking for an O2 sensor voltage drop as the air is pumped into the exhaust manifold. I'm sure it will soon trigger an error code if it's not working.
Well it looks like my car was suffering two separate problems. After a weeks driving the O2 sensor error codes haven't come back but the secondary air system codes on both banks have. There's no error message on the dash so it looks like that only gets triggered by the O2 sensor problem.
I'm now going to investigate the secondary air system using a hand vacuum pump, I suspect there is a leak or one of the valves isn't working as I can hear the pump working.
I'm now going to investigate the secondary air system using a hand vacuum pump, I suspect there is a leak or one of the valves isn't working as I can hear the pump working.
Attachments
My guess would be ...
A leak between the pump and the check valve so there is not enough pressure to open it..
A faulty check valve ..
Both heads have carboned up thereby blocking the air getting into the exhaust .
The system is only there to fast warm the cats and as such has no impact on the running of the engine .. save the planet stuff so it's not something you would want to throw a lot of money at .
A leak between the pump and the check valve so there is not enough pressure to open it..
A faulty check valve ..
Both heads have carboned up thereby blocking the air getting into the exhaust .
The system is only there to fast warm the cats and as such has no impact on the running of the engine .. save the planet stuff so it's not something you would want to throw a lot of money at .
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