B1990 Mercedes-Benz OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.
Some problems such as misfires and evaporative emission (EVAP) leaks can be very challenging to nail down. Misfires can be caused by ignition problems, fuel problems or compression problems. The underlying cause might be fouled spark plugs, bad plug wires, a weak ignition coil, dirty injectors, a shorted or open injector, low fuel pressure, a vacuum leak, a leaky head gasket, burned exhaust valve or a camshaft with a bad lobe.
Power Steering Pressure (PSP) Switch Malfunction In Key On, Engine Off Self-Test, this DTC indicates the PSP input to the PCM is high. In Key On, Engine Running Self-Test, this DTC indicates that the PSP input did not change state. Steering wheel must be turned during Key On, Engine Running Self-Test PSP switch/shorting bar damaged SIG RTN circuit open PSP circuit open or shorted to SIGRTN PCM damaged.
B1990 Mercedes-Benz Trouble Repair :
The rule of B1990 Mercedes-Benz code when it comes to emissions-related vehicle repair is that any modification that changes the vehicle from a certified configuration to a non-certified configuration is considered tampering: this applies to both vehicle owners and repair facilities and is, therefore, a Federal offense. Replacing a catalyst with a straight pipe is one traditional example. Likewise, overriding the OBD 2 system through the use of high-tech defeat devices or non-certified computer chips, for example, would also be considered tampering. The OBD system may, however, be repaired back to its original certified configuration with certified performance chips or appropriate aftermarket parts. |
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