Fuel System > Engine Control System > P0261 Cylinder 1 Injector Circuit Low

Component Location

General Description

Based on information from various sensors, the PCM calculates 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 PCM controls each injector by grounding the control circuit. When the PCM energizes the injector by grounding the control circuit, the circuit voltage should be low (theoretically 0V) and the fuel is injected. When the PCM de-energizes the injector by opening the control circuit, the fuel injector is closed and circuit voltage should momentarily peak.

DTC Description

Checking output signals from injectors under detecting condition, if an output signal is low, PCM sets P0261. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition

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

•

PCM

Enable condition

•	Engine running

•	11V ≤ Battery voltage ≤ 16V

•	No disabling faults present

•	Above conditions are met > 0.5sec.

threshold value

•	Open or short to ground

diagnosis time

•	Continuous

MIL ON condition

•	2 driving cycles

Specification

Item	Coil resistance(Ω)
Injector	11.4 ~ 12.6Ω ( at 20°C/ 68°F)

Schematic Diagram

Signal Wavefrom And Data

When the PCM energizes the injector by grounding control circuit, the circuit voltage should be low (theoretically 0V) and the fuel is injected. When the PCM de-energizes the injector by opening control circuit, the fuel injector is closed and circuit voltage should momentarily peak.

Monitor DTC Status

Check DTC Status

(1)	Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)	Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.

(4)	Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

	▶ Go to "Terminal and connector inspection" procedure.
	▶ Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Terminal And Connector Inspection

1.	Many malfunctions in the electrical system are caused by poor harness and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
	▶ Go to "Power Circuit Inspection" procedure.

Power Circuit Inspection

■ Check Voltage

1.	IG "ON" and disconnect injector connector.

2.	IG "ON" and ENG "OFF"

Measure voltage between power terminal of injector harness connector and chassis ground.

Specification : Approx. B+

Is the measured voltage within specification?

	▶ Go to "Control Circuit Inspection" procedure.
	▶ Check open or connection of the fuse connected to injector power supply. ▶ Repair open or short to ground in harness, and go to "Verification of Vehicle Repair' procedure.

Control Circuit Inspection

■ Check short to ground in harness

1.	IG "OFF" and disconnect injector connector and PCM connector.

Measure resistance between injector control terminal of injector harness connector and chassis ground.

Specification : Infinite

Is the measured resistance within specification?

	▶ Go to "Check open in harness" as follows.
	▶ Repair short to ground in harness, and go to "Verification of Vehicle Repair" procedure.

■ Check open in harness

1.	IG "OFF" and disconnect injector connector and PCM connector.

Measure resistance between injector control terminal of injector harness connector and injector control terminal of PCM harness connector.

Specification : Below 1Ω

Is the measured resistance within specification?

	▶ Go to "Component Inspection" procedure.
	▶ Repair open in harness, and go to "Verification of Vehicle Repair" procedure.

Component Inspection

■ Check injector

1.	IG "OFF" and disconnect injector connector.

Measure resistance between power and control terminals of injector connector.(Component side)

Specification : 11.4 ~ 12.6Ω ( at 20°C/ 68°F)

Is the measured resistance within specification?

	▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
	▶ Substitute with a known - good injector and check for proper operation. If the problem is corrected, replace injector and go to "Verification of Vehicle Repair" procedure.

There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. After testing PCM on the vehicle, use this function to reuse the PCM on the others.

Verification Of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scantool and select "DTC" button.

2.	Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.	Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

	▶ System performing to specification at this time. Clear the DTC
	▶ Go to the applicable troubleshooting procedure.