P1A77 Diagnostic Trouble Code

P1A77 is a kind of OBD-II Diagnostic P-Powertrain 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 P1A77 diagnostic trouble code may include:

Faulty or damaged wiring
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly
Poor fuel economy
Diminished fuel efficiency

Possible Causes :

The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
Defective ECU strategies or components will prevent proper regeneration
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.

Repair Processes :

Look at the plug wires to make sure they are not burnt or laying on the exhaust. 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. Now, clear the codes and test-drive the vehicle to see if the code is reset.

Process Tips

Diagnostic trouble code P1A77 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 P1A77.

Fortunately, P1A77 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P1A77 Trouble Code For Specific Cars

P1A77 Daewoo Evanda Fuel Volume Regulator Control Circuit/Open
P1A77 Daimler Double Six Heated Backlite Input Circuit Failure
P1A77 Changhe Ideal Door Lock Cylinder Circuit Short To Battery
P1A77 Cadillac Cimarron Decklid Ajar Rear Door Circuit Open
P1A77 Mercedes A 170 ABS Fluid Dumping Exceeds Maximum Timing
P1A77 Sovam 1100 Lamp Backup Switch Input Circuit Open
P1A77 Fiat Esv Lamp Seat Belt Circuit Short To Battery