DTC EFI-45X, EFI-543, EFI-545, EFI-55X

EFI-451 Misfire emission level cylinder 1
EFI-452 Misfire emission level cylinder 2
EFI-453 Misfire emission level cylinder 3
EFI-454 Misfire emission level cylinder 4
EFI-455 Misfire emission level cylinder 5
EFI-543 Misfire emission level from at least 1 cylinder
EFI-551 Misfire with three-way catalytic converter (TWC) damage cylinder 1
EFI-552 Misfire with three-way catalytic converter (TWC) damage cylinder 2
EFI-553 Misfire with three-way catalytic converter (TWC) damage cylinder 3
EFI-554 Misfire with three-way catalytic converter (TWC) damage cylinder 4
EFI-555 Misfire with three-way catalytic converter (TWC) damage cylinder 5
EFI-545 Misfire with three-way catalytic converter (TWC) damage from atleast 1 cylinder

Trouble Code Conditions

Diagnostic trouble code EFI-45X, EFI-543:
- If the engine control module (ECM) registers more than 0.5% misfires in 1,000 Engine revolutions (2,5OO ignition sequences), the engine control module checks whether this misfiring comes from one specific cylinder or from different cylinders. If only one cylinder exceeds the limit, diagnostic trouble code (DTC) EFI-543 is set first, followed by one of diagnostic trouble codes EFI-451, EFI-452, EFI-453, EFI-454 or EFI-455 depending on the cylinder. If more than one cylinder exceeds the limit diagnostic trouble code EFI-543 is stored with a diagnostic trouble code for the relevant cylinder.

Diagnostic trouble code EFI-55X, EFI-545:
- If the engine control module registers misfiring to such a degree that the three-way catalytic converter (TWC) could be damaged (this degree varies with engine speed and load), for 200 engine revolutions (500 ignition sequences) the engine control module checks whether the misfiring is coming from a specific cylinder or from different cylinders. If only one cylinder exceeds the limits, then one of diagnostic trouble codes EFI-4511, EFI-452, EFI-453, EFI-454 or EFI-455 and EFI-543, first diagnostic trouble code EFI-545 and then one of diagnostic trouble codes EFI-551, EFI552, EFI-553, EFI-554 or EFI-555 depending on the cylinder. If more than one cylinder exceeds the limit diagnostic trouble code EFI-545 is stored with a diagnostic trouble code for the relevant cylinder.

Substitute value(s)

Diagnostic trouble code EFI-55X, EFI-543:
- Fuel trim with rear heated oxygen sensor (HO2S) disabled.
- Long-term fuel trim disabled.
- Three-way catalytic converter diagnostic disabled heated oxygen sensor diagnostic disabled.

Diagnostic trouble code EFI-55X, EFI-545:
- Fuel trim for both heated oxygen sensors disabled.
- Heated oxygen sensor aging diagnostic disabled long-term fuel trim disabled.
- Three-way catalytic converter diagnostic disabled.
- EVAP diagnostic disabled.
- Short-circuit in heated oxygen sensor signal cable and ground lead blocked.

Possible source(s)
- Defective sparkplugs, ignition cables, distributor cap/rotor, ignition coil or flywheel/pulse wheel.
- Blocked/leaking injector.
- Uneven compression.
- Leakage between cooling system and cylinder.
- Moisture, flashover in ignition system HT side intermittent open-circuit,intermittent short-circuit to ground, intermittent short-circuit to voltage supply, contact resistance or loose connection in ignition system low tension side,in injector circuit or fuel pump circuit.
- Engine oil level too high.
- Air leakage.
- Fuel pressure and residual pressure.

Fault Causes Not Included In The Fault-tracing Process, But Which May Still Post A Diagnostic Trouble Code:
- Fuel stoppage.
- Water in spark plug wells.
- Contaminated fuel or incorrect fuel.
- Repeated cold starting where the engine coolant temperature is not allowed to reach operating temperature between starts.

Fault symptom(s)
- Engine does not start, or is difficult to start.
- Engine runs unevenly at idling speed, or jerkily while driving.
- Poorer performance.
- High emissions.
- Glowing pieces of three-way catalytic converter falling out of the exhaust pipe.