Injector Testing and EFI Self Diagnosis Codes

Today I completed testing of Injectors and learned how to read codes sent from ECU to identify faults.

Injector Testing

The first Test I did was the Testing of Injectors this was done in 3 different ways; using a screwdriver to check if injectors were pulsing, Using a Logic probe to show pulses, (the one I made earlier) and using a multimeter set on duty cycle. 

The most accurate test of the 3 was using the multimeter set on duty cycle. As this showed a more accurate amount of time that the injectors were active. (duty cycle) According to the readings displayed on the ohmmeter, when the car was idling the injectors were active around 5% of the time and when car was revving higher this increased to around 50% of the time.

Using the other 2 methods were far less accurate because they only showed that the injectors are working as only a sound or flashing of LED. This did not show the exact way injectors were functioning. 

EFI Self Diagnosis Codes

The second test was done by reading diagnostic codes from the ECU when a fault was occurring.

This was done using the check engine light, on the cars dashboard and using it to signal a fault code. This was done by bridging 2 terminals on the diagnostic plug. The terminals were TE1 to E1. Then observing the code as the check engine light flashed it on the dashboard. It indicates this by flashes then pauses.

Example of Diagnostic code flashing. this one is showing code "31" 

(3 flashes short pause then single flash)

which indicates a MAP sensor problem

The circuit that needed repairing was the water temperature circuit (code "22") as indicated by the check engine light. To repair this the sensor will need to be checked using a heat source and a ohmmeter and taking readings of the resistance at cold and hot by heating the sensor. Resistance should decrease as water temperature increases. If it was not doing this the sensor will be malfunctioning and will need to be replaced with a good sensor.

If it is not replaced this would cause the sensor to send incorrect readings to the ECU and the injectors will not be delivering the correct air fuel ratio at the right time and would cause the engine to run rich, decreasing the engine efficiency.