Based on information from various sensors, the ECM measures the fuel injection amount. The fuel injector is a solenoid-operated valve and the fuel injection amount is controlled by length of time the fuel injector is held open. The ECM controls each injector by grounding the control circuit. When the ECM energizes the injector by grounding the control circuit, the circuit voltage should be low (theoretically 0V) and the fuel is injected. When the ECM de-energizes the injector by opening the control circuit, the fuel injector is closed and circuit voltage should momentarily peak.
Checking output signals from injectors. Under detecting condition, if an output signal is low, ECM sets P0261.
Item
Detecting Condition
Possible Cause
DTC Strategy
Signal Low
Poor connection
Open or short to ground in power harness
Open or short to ground in control harness
Injector
ECM
Enable Conditions
Engine running state
11V = Battery voltage = 16V
Above conditions are met > 0.5sec.
Threshold value
Open or short to ground
Diagnosis Time
Continuous (more than 5 sec. failure for every 10 sec.test)
MIL On Condition
3 Driving Cycles
Coil resistance(?)
13.8 ~ 15.2 [20?(68?)]
Fig.1) Normal waveforms of Injector under idle condition.
When the ECM energizes the injector by grounding control circuit, the circuit voltage should be low (theoretically 0V) and the fuel is injected. When the ECM de-energizes the injector by opening control circuit, the fuel injector is closed and circuit voltage should be peak at a moment.