Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information

Condition
Engine control module (ECM) monitors continuously that the engine can provide the vehicle's brake boosters with sufficient vacuum. To do this, the Engine control module (ECM) uses a number of different signals such as, e.g., air pressure in the intake manifold, the ambient air pressure, amount of air drawn into the engine, the engine rpm, and the accelerator pedal's position. If Engine control module (ECM) registers that the difference between air pressure in the intake manifold and ambient air pressure is too small or that air flow into the engine is too high for 5.1 seconds, when the accelerator pedal is let up and engine rpm is higher than 700 rpm, then diagnostic trouble code ECM-9818, Too low vacuum, is stored.
For upgraded software, released during year 2006 or later, certain adjustments have been made. Both too low pressure difference and too high air flow are required for generation of the diagnostic trouble code.

Substitute value

Cruise control off.
Cruise control off during entire operating cycle in which fault was detected. If the fault is no longer present, the function is available the next time the car is started.

Fuel cut-off that follows accelerator pedal position.
Engine speed is regulated via fuel cut-off by deactivating the injectors one at a time. The engine speed is decided by the accelerator pedal position sensor's position and the speed is maximized to approx. 2000 rpm. This reconfiguration can cause the engine to idle very unevenly since the engine control module (ECM) regulates engine speed by cutting of the fuel to the cylinders individually. Do not confuse this reconfiguration (engine behavior) with an actual driveability problem that was present before reconfiguration.
For upgraded software, released in 2006 or later, adjustments have been made to substitute values. For this fault, no replacement values will be activated.

Possible source

Incorrect signal:
- air leakage after the throttle.
This diagnostic trouble code is generated in combination with other trouble codes. Information on the possible root cause is described.

Fault symptom[s]
- uneven idle
- worse performance at maximum speed.