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Diagnostický případ
Opravené vozidlo
Neglected vehicle service and bad luck
21.04.2016
27265x
Informace o vozidle
| VIN: | WDD2193221A099624 |
| Výrobce: | Mercedes-Benz |
| Model: | CLS |
| Rok výroby: | 2006 |
| Kód motoru: | 3,0 320 CDI |
| Typ motoru: | |
| Výkon (kW): | 165 kW |
| Převodovka: | Automatická |
| Palivo: | Diesel |
| Najeto: | 260 151 km |
- během jízdy
- [2078-002] Check component B28/8 (Pressure differential sensor (DPF)). The signal voltage is too low.
- [2270-002] N14/3 (Glow time output stage) , NONE Supply voltage
- [2626-001] Diesel particulate filter The soot content of the particulate filter is too high for regeneration.
- [912D] The preglow lamp is faulty.
- trvalá závada
- sporadická závada
Doposud provedeno bez úspěchu
The previous workshop replaced glow plugs.Závěr
VOZIDLO JSEM NEOPRAVOVALThe DPF differential pressure sensor was replaced. The pre-glow control unit was replaced and the brake pedal/light switch was replaced. I managed to bypass the saturated DPF filter that was reporting that regeneration is not possible. I tricked the system by lowering the differential pressure sensor signal at idle. After this it was possible to erase the DTC reporting a saturated DPF filter. Now I went for a test drive. I started driving slowly at first and then incresed to a steady speed of 80-90 km/h. I was surprised that normal DPF filter regeneration was launched without activating the service regeneration.
The DPF filter was regenerated and filter saturation dropped to 7 mg.
Obrázky, fotografie a soubory
MB CLS 320 Cdi has several problems... (6934/1)
The rear bumper is black from fine soot. The MIL light is ON. The engine is in limp-home mode and has no power. Several DTCs are stored in memory.
No comment (6934/2)
I don't know how a customer can overlook a service reminder that is 1718 days overdue...
The ECU is not switching pre-glow current to the plugs - onboard diagnostics are reporting - test OK. (6934/3)
The DTC message "2270-002 N14/3 (Glow time output stage), NONE Supply voltage" was correct. The actuator test reported an OK result with a note that a non-erasable DTC is stored in memory.The TEXVIK was used to test all signals (12V power supply, ground 0V, LIN BUS signal - all OK). No current is flowing during the test into the control unit or out to the glow plugs.
ABR Adaptive Brake system is reporting a defective brake light switch and the brake lights turn ON (6934/4)
Despite the working brake lights the DTC is quoting "430A Test component S9/1 (Stop lamp switch)". This component has two pairs of contacts. One for the lights (this is working and the second is for the engine ECU (position state. This "status" signal when the brake pedal was pressed was not active on the TEXVIK display.
The onboard diagnostics are showing a permanent differential pressure sensor value of 19 hPa! (6934/5)
The 19 hPa is a substitute value calculated by the ECU if the differential pressure sensor voltage is out of range. I connected a resistance box and simulated a zero differential pressure value (0hPa)at ignition ON state by adjusting a resistance value of 610 kOhms on the resistance box. The DTC is reporting a defective sensor fault that can't be erased. This fact confirms that all the wiring and ECU are OK.Conversion: 1 Bar = 1.000 hPa = 100.000 Pa = 100 kPa
The previous workshop also replaced several failed components... (6934/6)
All glow plugs and leaking turbocharger gaskets were replaced.
Despite an installed DPF filter the exhaust contains fine soot particles... (6934/7)
At idle the engine is suffering to run and with high pressure it is pushing fine particles into the exhaust.
Simulation directly on the differential pressure sensor wiring (6934/8)
I was lazy to identify the individual pins so used the measured values. One 5 V, twice 0 V and one wiring circuit could not be changed even by connecting low value voltage. This was the ground.With the help of the resistance box I interconnected 5 V to the signal line and simulated a value of 0 hPa that was shown by the onboard diagnostics.
LOG recording with resistance box connected (6934/9)
Yellow = differential pressure value recorded by the Launch X-431 GDS scan tool.The applied 610 kOhm to the signal line simulates an output voltage value of about 0.63 V and 0 hPa pressure value for the onboard diagnostics.
2 = 2 MOhms applied = "3" = 19 hPa a represents a limp-home condition and an illuminated MIL light.
3 = Substitute value 19 hPa generated by the ECU.
4 = The ignition is switched OFF and ON and due to the applied 610 kOhms the displayed pressure value is 0 hPa.
5 = 2 MOhms reapplied but just before point 5 a value of 1 MOhm was applied. This was not enough to activate a limp-home condition or a DTC..
3a = After recording an out of range value (5) the substitute value of 19 hPa is activated again.
1a = When the ignition is turned off and 610 kOhms is reapplied a simulated value of 0 hPa is displayed and the DTC stored in memory diasappears..
DTC sets when a value below 0.2 V is detected (6934/10)
Channel designation:Ch. 1 – brown = 5 V ref. voltage from the engine ECU
Ch. 2 – blue = modulated signal voltage (simulated)
Conditions: as on previous picture
Description: as on previous picture
Documentation of simulated voltage when no DTC was set (left) and when a DTC was set (right).
TEXVIK analysis of the pre-glow control unit signals (6934/12)
Recording: LIN BUS signal, power supply for the pre-glow system electronics, ground for the pre-glow system electronics, pre-glow system el. current.
TEXVIK analysis of the pre-glow control unit signals (6934/13)
Channel designation:Ch. 1 – brown = LIN BUS
Ch. 2 – blue = ground of the pre-glow system electronics
Ch. 3 – light blue = 12 V power supply of the pre-glow system electrinics
Ch. 4 – grey = el. current for the pre-glow system
Measured during: actutor test
Description: During the actuator test no el. current is flowing through the system...
The new trick worked (6934/14)
Yellow = temperature in front of the DPF filter - measured during a constant speed of 90km/hAfter replacing the defective components it was necessary to solve the problem with the saturated DPF filter. On the new differential pressure sensor I simulated a lower voltage at idle and after several starts it was possible to erase DTC (2626-001).
While driving at a constant speed and with a strong hissing sound from the saturated DPF filter I managed to enable a regeneration mode. Afzer a very short time the DPF temperature increased above 600°C and the soot was burned of to a value of 7 mg! The vehicle regained power, no DTC were recorded and the DPF filter doesn't require removal and cleaning.
Soubory ke stažení
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mwfTEXVIK recording – DTC sets when a value below 0.2 V is detected (6934/11).mwf Channel designation:Stáhnout soubor
Ch. 1 – brown = 5 V ref. voltage from the engine ECU
Ch. 2 – blue = modulated signal voltage (simulated)
Conditions: same as previous picture
Description: same as previous picture
Documentation of simulated voltage when no DTC was set (left) and when a DTC was set (right).
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