C1603 Diagnostic Trouble Code

C1603 is a kind of OBD-II Diagnostic C-Chassis Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a C1603 diagnostic trouble code may include:

Cherry red hot catalytic converter
Poor acceleration
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Reduction in engine performance, especially at low RPM levels

Possible Causes :

A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.
Some aftermarket accessories and performance modifications
An air leak forward of the DPF will change the sensor readings resulting in the code

Repair Processes :

With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications.

Process Tips

Diagnostic trouble code C1603 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before C1603.

Fortunately, C1603 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C1603 Trouble Code For Specific Cars

C1603 Suminoe Flying MAF Sensor In Range But Lower Than Expected
C1603 American Gadabout Air Suspension Height Sensor Power Circuit Failure
C1603 Buick Le Sabre Cylinder 8 Injector Circuit Low
C1603 Renault R5 Heated Wind Shield Relay Short to Vbatt (changed from Failure 2/6/97)
C1603 Jaguar Xka Seat Driver Rear Down Circuit Failure
C1603 Mitsubishi Dangan Audio Steering Wheel Switch Circuit Fault
C1603 Rover P2 Ignition Coil Primary/Secondary Circuit Malfunction