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P1492

Read the instructions below then start the fault diagnostic procedure.

Symptom: CHECK ENGINE. Possible faulty reading on the fuel gauge in MIU.

P1492


EVAP Tank Pressure Sens. Value too low when Depressurised and malfunctional fuel level sen


Fault symptoms


• CHECK ENGINE.

• Possible faulty reading on the fuel gauge in MIU.


On-Board Diagnostics

Type of diagnosis:


- Once per driving cycle. Interrupted when fault criteria fulfilled or OK reported. Restarts next driving cycle.


Enable criteria:


- General conditions for this trouble code: Atmospheric pressure must exceed 72 kPa and the engine coolant and intake air temperature must exceed -7°C.

- Accepted transition diagnosis of oxygen sensor 1. Purge active. Idling. Max. one change in status of brake light switch. Purge adaptation higher than -7%. Car stationary for 8 s.

The diagnosis will start once the above conditions have been fulfilled. If the diagnosis is interrupted then the speed must exceed 0 on one occasion before it is allowed to restart.


Fault criteria:


- The adaptation limit of the tank pressure has changed more than 1.0 kPa.


Generation of diagnostic trouble codes:


- Fuel level, Plausibility diagnosis: Because fuel level is used as an enable criteria in certain diagnosis, then the control module must know that fuel level value is plausible. It works in such a way that Trionic receives the bus message ”Fuel level XX litre" from MIU. While driving Trionic observes the value and as the vehicle is driving it is consuming petrol, Trionic sees that the fuel level value will fall. In Trionic there is a number of filtrations of the value so as to avoid inaccuracies due to for example splashing fuel in the tank and hill starts. The fuel level diagnosis can be said to be a support diagnosis, it does not generate its own diagnostic trouble codes, but if for example the tank pressure sensor diagnosis has reported a performance problem (e.g. low value) in the tank pressure sensor then DTC P1452 is normally generated. If on the other hand the tank pressure sensor diagnosis has reported the same fault and the fuel level diagnosis at the same time has also reported a fault then DTC P1492 is generated instead.

Diagnostic trouble codes are generated when the fault criteria are fulfilled and the dependents are OK.


Dependents:


- P0444, P0445, P0501, P0502, P0506, P0507, P1444, P1445, P1576 and P1577.


System reaction to a fault:



- Integrity diagnosis of purge system blocked. Purge and fuel adaptation blocked.


OK report:


- Diagnoses for P1451, P1452 and P1453 performed once and fault criteria not fulfilled. Fault criteria for P0452 or P0453 not fulfilled.


Fault handling: (For more information, see Fault handling III, other emission-related components and functions .)


- Type III.


Diagnostic help

Fault diagnosis concerns checking tank pressure equalization to atmosphere or electrical fault in connecting leads or in the sensor.

Functions in the diagnostic tool related to the fault:


• Diagnostic status for the diagnosis.

• Pressure sensor value, unit kPa. The value should be about 0 kPa when the filler cap is removed.


For more information, see Fault diagnosis, general.

Check the wiring

Jiggle the leads and in-line connectors at various points and in different directions to detect any intermittent breaks or short circuits in the wiring. Observe the multimeter, test lamp or diagnostic tool while doing this.