C1040 Diagnostic Trouble Code

C1040 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 C1040 diagnostic trouble code may include:

Poor fuel economy
Possible spark knock (detonation / pre-ignition)
Misfire
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

Possible Causes :

A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.
Faulty IMRC actuator/sensor
A plugged converter will cause of host of driveability problems as well as set this code. A severely plugged converter will result in the inability to increase rpm when under load. Look for a code such as P0421 -- catalytic converter efficiency below threshold if the converter indicating a faulty converter.

Repair Processes :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness.

Process Tips

Diagnostic trouble code C1040 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 C1040.

Fortunately, C1040 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C1040 Trouble Code For Specific Cars

C1040 Daihatsu Domino Gear Shift Position Circuit Intermittent
C1040 Nissan Armada Climate Control Air Temperature Internal Sensor Motor Circuit Failure
C1040 Allard Monte Carlo Air Bag Driver Circuit Short To Ground
C1040 Nag Voran Camshaft Position Sensor Circuit Low Input
C1040 Mercedes R 350 Accessory Delay Relay Coil Circuit Open
C1040 Renault 18 Gear 3 Incorrect ratio
C1040 Mercedes Slk 300 Air Bag Diagnostic Monitor Ground Circuit Short To Ground