C1977 Diagnostic Trouble Code

C1977 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 C1977 diagnostic trouble code may include:

Malfunction Indicator Lamp (MIL) illuminated
Carbon Buildup on O2 Sensor
Poor fuel economy
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.

Possible Causes :

An air leak forward of the DPF will change the sensor readings resulting in the code
Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.
Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.

Repair Processes :

If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed. Look for damage to the tank indicating impact that may have damaged the fuel pump or sender.

Process Tips

Diagnostic trouble code C1977 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 C1977.

Fortunately, C1977 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P1205 Trouble Code For Specific Cars

C1977 Skoda Montreux Knock Sensor 1 Circuit low Input (Bank 1 or Single Sensor)
C1977 Chevrolet Uplander Engine Coolant Level Switch Circuit Short to Ground
C1977 Awz-zwickau Trabant Aux Heater Overheat Sensor Circuit Short to Ground
C1977 Jaguar Xj-12 Seat Driver Front Up Circuit Short To Ground
C1977 Talbot 25 Mirror Passenger Horizontal Feedback Potentiometer Circuit Failure
C1977 Ram 2500 Fuel Temperature Sensor B Circuit High Input
C1977 Monteverdi Hai Battery Power Relay Circuit Short To Ground