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.

C1977 Trouble Code For Specific Cars

C1977 Audi A8 ANTI THEFT HORN OUTPUT CIRCUIT Short to Gnd
C1977 Lotec Sirius Torque Converter Clutch Circuit Malfuction
C1977 Mercedes E 200 ABS Power Relay Coil Circuit Failure
C1977 Jeep Renegade Seat Driver Recline Backward Circuit Open
C1977 Chevrolet Equinox 3 Driver's Seat Seatback Autoglide Forward Switch Circuit Short to Ground
C1977 Lagonda 2.5-litre Shift Solenoid D Control Circuit Range/Performance
C1977 Holden Fb Port Air Circuit Malfunction/ (AIR) System Bank 2