Code does not indicated a faulty or unplugged ECT.
DTC P0125 : INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP FUEL
CONTROL (EXCEPT CALIF. EMISSIONS)
CAUTION : If ECM replacement is instructed in following testing,
always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction.
NOTE:
Heated oxygen sensor No. 1 refers to oxygen sensor closest to engine block. Heated oxygen sensor No. 2 refers to oxygen sensor farthest from engine block.
Circuit Description
Heated oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to determine fuel injection system operation. Heated oxygen sensors include a heater. DTC is set when heated oxygen sensor No. 1 does not output a rich condition once engine is at normal operating temperature, engine speed of more than 1500 RPM and vehicle speed is 25-62 MPH for at least 2
minutes. Possible causes are:
i) Heated oxygen sensor No. 1 circuit is open or shorted.
Ii) Defective heated oxygen sensor No. 1.
Iii) Air induction system malfunction.
Iv) EGR system malfunction (if equipped).
V) Improper fuel pressure.
Vi) Defective fuel injector.
Vii) Exhaust system leak.
Viii) Vehicle run out of fuel.
Ix) Defective ECM.
Diagnostic Aids
After confirming DTC P0125, use scan tool to access CURRENT DATA to confirm voltage output of heated oxygen sensor No. 1. If voltage displayed on scan tool is always less than 0.1 volt, circuit may be open or shorted. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.
Diagnosis & Repair
1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0125 is displayed, go to next step.
2. Connect scan tool to Data Link Connector (DLC) No. 3. Start and
warm engine to normal operating temperature. Using scan tool, monitor heated oxygen sensor No. 1 output voltage. Snap accelerate engine to about 4000 RPM 3 times. Heated oxygen sensor No. 1 should indicate a rich signal (.45 volt or more) at least once. If a rich signal is indicated for heated oxygen sensor No. 1 at least once, go to step 10. If either heated oxygen sensor No. 1 does not display a rich signal at least once, go to next step.
3. Check for open or short in wiring between heated oxygen sensor No. 1 and ECM. If problem does not exist, go to next step. If problem exists, repair wiring as necessary.
4. Using scan tool, check if a misfire has occurred by monitoring DTCs and DATA LIST. If a misfire has occurred, perform DTC P0300: RANDOM MISFIRE DETECTED. If misfire has not occurred, go to next step.
5. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
6. Check EGR system components (if equipped). If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Check fuel pressure. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
8. Check fuel injectors. If problem exists, repair as necessary. If
problem does not exist, go to next step.
9. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, replace defective heated oxygen sensor No. 1.
10. Perform test drive confirmation, then go to next step.
11. Clear and recheck for DTCs. If DTC P0125 is displayed again, replace ECM. If DTC P0125 is not displayed again, go to next step.
12. Vehicle either ran out of fuel problem is intermittent. Check component and ECM connections.
Wednesday, August 17th, 2011 AT 4:10 PM
