My C 200 CDI (122 hp, 2005) OM646 diesel engine had the Engine Warning Light on for a while. Also the 3000 rpm limiter (1st level limp mode) was active. I replaced the Air Flow Mass meter unit and air filter. Both were quite dirty. The engine then run normally for a few days. But then the rpm limiter began to activate again. Not on every trip, but especially when the car is more heavily loaded with passengers or a trailer.
So I started to monitor the engine fault codes with an ELM327 OBD II device. Here:
P2509 ECM/PCM Power Input Signal Intermittent (or Additional Heater fault) - always comes up.
P2359 boost pressure control maximum exceeded - 2nd most frequent fault code.
P0299 Turbo Underboost Condition – when driven with higher loads. Occurs together with 3000 rpm limitation.
P0234 Engine Overboost Condition – occurred just one or two times, when driven with higher loads. Occurs together with 3000 rpm limitation.
P2632 Exhaust gas pressure sensor/turbocharger boost pressure actuator boost pressure fault – so far occurred only once.
I have cleared the fault codes after each trip. The Engine Warning Light has not come on since the AFM replacement.
Puzzled at the occurrence of both overboost and underboost fault codes, I then went to a DIY guy with a Star tester to check the boost values. At 3000 rpm stationary, the boost was 1015 hPa (code 4609, should be about 1250 hPa) while the boost regulator was at 95% (code 230, should be <= 90%). Ambient air pressure was 991 hPa and suction pressure (code 4611) 985 hPa.
This guy then suggested that the turbo unit is the culprit. But as this is an expensive part, I ask you for a second opinion: Any other possible causes? Boost pressure sensor?
I have seen a number of possible fault reasons including (for underboost indication) : faulty AFM, faulty boost pressure sensor, leaking turbo hoses, faulty EGR valve, faulty adjustment motor for induction flaps, faulty vane adjuster in the turbo, low oil level in automatic transmission; and (for overboost indication) faulty wastegate solenoid or leaking wastegate hoses. And of course a faulty or clogged turbo.
Thanks for any advice that can help me pinpoint the fault;-)
The car has seen very light service, which according to some mechanics leads to soot deposits etc., which can be burned away by driving in high RPM for some time.
So I started to monitor the engine fault codes with an ELM327 OBD II device. Here:
P2509 ECM/PCM Power Input Signal Intermittent (or Additional Heater fault) - always comes up.
P2359 boost pressure control maximum exceeded - 2nd most frequent fault code.
P0299 Turbo Underboost Condition – when driven with higher loads. Occurs together with 3000 rpm limitation.
P0234 Engine Overboost Condition – occurred just one or two times, when driven with higher loads. Occurs together with 3000 rpm limitation.
P2632 Exhaust gas pressure sensor/turbocharger boost pressure actuator boost pressure fault – so far occurred only once.
I have cleared the fault codes after each trip. The Engine Warning Light has not come on since the AFM replacement.
Puzzled at the occurrence of both overboost and underboost fault codes, I then went to a DIY guy with a Star tester to check the boost values. At 3000 rpm stationary, the boost was 1015 hPa (code 4609, should be about 1250 hPa) while the boost regulator was at 95% (code 230, should be <= 90%). Ambient air pressure was 991 hPa and suction pressure (code 4611) 985 hPa.
This guy then suggested that the turbo unit is the culprit. But as this is an expensive part, I ask you for a second opinion: Any other possible causes? Boost pressure sensor?
I have seen a number of possible fault reasons including (for underboost indication) : faulty AFM, faulty boost pressure sensor, leaking turbo hoses, faulty EGR valve, faulty adjustment motor for induction flaps, faulty vane adjuster in the turbo, low oil level in automatic transmission; and (for overboost indication) faulty wastegate solenoid or leaking wastegate hoses. And of course a faulty or clogged turbo.
Thanks for any advice that can help me pinpoint the fault;-)
The car has seen very light service, which according to some mechanics leads to soot deposits etc., which can be burned away by driving in high RPM for some time.
