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Hi All, dealer wanted almost $1000 to diagnose a check engine light after the initial fee of $230 didn't yield any results; I decided to decline since it seemed excessive. This is what they found (or not):
CHECK ENGINE LIGHT ON. PERFORM SDS QUICK TEST FOUND THAT THE LIGHT ON DUE TO A CODE 201C TANK PRESSURE SENSOR PERFORM VISUAL INSPECTION FOUND THAT THE SENSOR IS NOT DAMAGED . PERFORM VOLTAGE AND GROUND CHECK AT THE SENSOR. CHECK OK PERFORM SMOKE CHECK ON THE FUEL SYSTEM. CHECK OK . PERFORM VACUUM AND PRESSURE TEST ON THE FUEL TANK AND THE FUEL TANK CHECKS OK , PRESSURE SENSOR IS READING CORRECTLY.
Anybody have any ideas what could cause the CEL? The sensor that is throwing the code seems to be fine. Also the cruise control distronic, blind spot and pre-safe are disabled, so maybe a faulty circuit board? Unlikely that all fuses are blown at the same time?
Hi All, dealer wanted almost $1000 to diagnose a check engine light after the initial fee of $230 didn't yield any results; I decided to decline since it seemed excessive. This is what they found (or not):
CHECK ENGINE LIGHT ON.....
PERFORM SDS QUICK TEST FOUND THAT THE LIGHT ON DUE TO A CODE 201C TANK PRESSURE SENSOR
PERFORM VISUAL INSPECTION FOUND THAT THE SENSOR IS NOT DAMAGED.
PERFORM VOLTAGE AND GROUND CHECK AT THE SENSOR.
CHECK OK PERFORM SMOKE CHECK ON THE FUEL SYSTEM. CHECK OK .
PERFORM VACUUM AND PRESSURE TEST ON THE FUEL TANK AND THE FUEL TANK CHECKS OK
PRESSURE SENSOR IS READING CORRECTLY.
Anybody have any ideas what could cause the CEL?
The sensor that is throwing the code seems to be fine.
Also the cruise control distronic, blind spot and pre-safe are disabled, so maybe a faulty circuit board?
Unlikely that all fuses are blown at the same time?
> RECAP:
You are saying "the cruise control distronic, blind spot and pre-safe are disabled" concurrently by some type of fault at the same time as your "tank pressure sensor" circuit going crazy, right ?
Your dealer diagnostic work is a real deal for $230. They did quite a bit of good testing if they really did the reported work. It seems a bit disproportionate but let's say we trust that for now.
> NORMAL :
Based on that mix, I think you may be dealing with a transient condition brought by a LOW SYSTEM VOLTAGE.
These cars are extremely well built to produce these ghost faults. Engineered defects features are used to generate a cascade of marginal conditions. I call these "snowballs" or "Russian-Doles" for lack of better word to describe layered strings of disfunctions.
For some reason the Bosch ECU commands dismal ALT output voltage, that soft-crashes the R-SAM, that impacts the tank sensors, that impacts LPFP pump pressure output, that starves the HPFP, that causes lean engine hesitations when rich mixtures are required for accelerations... ouch!
I am pretty much positive the bumper radars are NOT involved here because they can mess up things up pretty good but not the fuel tank operations.
The amazing 3-Ph LPFP circuit with its carefully undersized ripple filtering is in charge of injecting noise into the harness thereby causing havoc with R-SAM communications.
> NEXT:
Pls scan your car with an iCarsoft, Autel or a similar handheld unit to get a list of faults.
We want to know what circuits faults are STORED (transients) and also CURRENT. Not all chaos contributors report faults. These reports are troubleshooting hints to help match known issues. Identifix dot com provides a database of fixes to professional shops.
> FREE RELIEF :
In the mean time, float charge your battery, reset faults, reboot car.
This is not a fix but will provide you with an easy temporary relief.
Last edited by CaliBenzDriver; Apr 17, 2023 at 01:52 PM.
Reason: relief not cure
Hi! Thank you for your thorough reply. I went ahead and scanned the car with my OBD scanner tool and the only stored code is P0450. I also included some pictures of the freeze frame when the code occurred. Hope this helps to further narrow down the problem.
I went ahead and scanned the car with my OBD scanner tool and the only stored code is P0450. I also included some pictures of the freeze frame when the code occurred.
Hope this helps to further narrow down the problem.
Great detective work! Now you've got the evidences to pin your issue.
It's 100% exactly as I have described above in post #2.
tank sensor gets jammed on the way to R-SAM ...
Easy driving at 65mph with engine at 1750rpm...
Smoking gun: 12.3V battery buster by Bosch ECU
The second installment of that story is about the uncontrolled voltage (12.3V... 11.xV) while driving, all without any related fault.
The tank sensor itself is genuinely fine. It's acting as decoy for the non-initiated technicians. It's an easy way to go around circles with no result.
> Tank pressure SNR:
A large signal mixed with a little bit of noise causes no problem but a lot of noise mixed with a small signal can drawn it. Significance of relative scales
When operating within range (14.9V to 12.6V) the noise is not significant enough but when operating under dismal voltage the noise can overtake a small signal.
Here our small signal of couple volts is the tank pressure signal. The two tank level sensors are also good candidate for disruption when near empty.... they will lie to R-SAM that computes the tank total level from both sides of split tank.
> What to do:
You may want to consider:
1-- disable the noise source within LPFP
2-- prevent runaway voltage control by ECU
3-- Both prongs together
I let you imagine these great cars run far better when the alternator powers up 100% of the load normally.
Last edited by CaliBenzDriver; Apr 17, 2023 at 04:38 PM.
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