DTC P0125 INSUFFICIENT COOLANT TEMP. FOR CLOSED LOOP FUEL CONTROL

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1 05196 DIGNOSTICS 057HO03 DTC 0125 INSUFFICIENT COOLNT TEM. FO CLOSED LOO FUEL CONTOL CICUIT DESCITION To obtain a high purification rate of the CO, HC and NOx components of the exhaust gas, a threeway catalytic converter is used. For the most efficient use of the threeway catalytic converter, the airfuel ratio must be precisely controlled so that it is always close to the stoichiometric airfuel ratio. The oxygen sensor has the characteristic that it provides output voltage* being approximately proportional to the existing airfuel ratio. The oxygen sensor output voltage* is used to provide feedback for the ECM to control the airfuel ratio. y the oxygen sensor output, the ECM can determine the deviation amount from the stoichiometric airfuel ratio and control the proper injection time immediately. If the oxygen sensor is out of order, ECM is unable to perform the accurate airfuel ratio control. The oxygen sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), the current flows to the heater to heat the sensor for the accurate oxygen concentration detection. *: The voltage value changes at the inside of the ECM only. Ideal irfuel Mixture Heater Solid Electrolyte (Zirconia Element) Output Voltage Element Cover latinum Electrode Exhaust Gas Section ir icher ir Fuel atio Leaner DTC No DTC Detecting Condition Trouble rea 0125 fter engine is warmed up, oxygen sensor output* does not change when conditions (a), (b), (c) and (d) continue for at least 1.5 min: *: Output value changes at inside of the ECM only (a) Engine speed: 1,500 rpm or more (b) Vehicle speed: km/h (25 62 mph) (c) Throttle valve is not fully closed (d) 140 sec. or more after starting engine CV hose Open or short in oxygen sensor circuit Oxygen sensor ir induction system Fuel pressure Injector Gas leak on exhaust system ECM fter confirming DTC 0125, use the hand held tester or OD II scan tool to confirm output voltage of the oxygen sensor from the CUENT DT COOLL MTIX (M940U) uthor : 396

2 DIGNOSTICS WII DIGM ECM 4 HT1 23 OX1 From Terminal 3 of E.F.I. elay 4 E5 HT1 IG2 9 IG OX1 W Center J/ IG HT OX Oxygen Sensor (ank 1 Sensor 1) 3 IG3 8 IG3 18 W IG3 9 2 (*2) 4 (*2) HT OX + Oxygen Sensor (ank 1 Sensor 2) 3 (*2) 1 (*2) J3 Junction Connector *1: Shielded *2: 2WD EC COOLL MTIX (M940U) uthor : 397

3 05198 DIGNOSTICS INSECTION OCEDUE ead freeze frame data using the handheld tester or OD II scan tool. ecause freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the airfuel ratio was lean or rich, etc. at the time of the malfunction. 1 ED OUTUT DTC(ESIDES 0125) esult: ESULT Only 0125 is output and other codes are output. If any other cord besides 0125 are output, perform the troubleshoot on that DTC before. GO TO ELEVNT DTC CHT 2 ED VLUE OF OD II SCN TOOL O HNDHELD TESTE(OUTUT VOLTGE OF OXYGEN SENSO) (a) Warm up the oxygen sensor with the engine speed at 2,500 rpm for approx. 90 sec. (b) Use the handheld tester or OD II scan tool to read the output voltage of the oxygen sensor during idling. Oxygen sensor output voltage: lternates repeatedly between less than 0.4 V and more than 0.55 V (See the following table) CHECK CONNECTION OF CV HOSE Go to step 10 EI O ELCE CV HOSE 2003 COOLL MTIX (M940U) uthor : 398

4 DIGNOSTICS CHECK WIE HNESS O CONNECTO(ECMOXYGEN SENSO) EI O ELCE WIE HNESS O CONNECTO 5 INSECT OXYGEN SENSO(OXYGEN SENSO HETE ESISTNCE) + HT (a) (b) Disconnect the oxygen sensor connector. Measure resistance between the terminals HT and + of the oxygen sensor. esistance: 5 10 Ω (20 C) OX ELCE OXYGEN SENSO 6 CHECK I INDUCTION SYSTEM (See page 1213) EI O ELCE I INDUCTION SYSTEM 7 CHECK FUEL ESSUE (See page 115) EI O ELCE FUEL SYSTEM 8 INSECT FUEL INJECTO SSY (See page 117) ELCE FUEL INJECTO SSY 9 CHECK EXHUST GS LEK EI O ELCE EXHUST GS LEKGE OINT ELCE OXYGEN SENSO 2003 COOLL MTIX (M940U) uthor : 399

5 05200 DIGNOSTICS 10 EFOM CONFIMTION DIVI TTEN GO 11 ED OUTUT DTC(ESIDES 0125) esult: ESULT 0125 is not output is output. CHECK FO INTEMITTENT OLEMS 12 CONFIM VEHICLE UNS OUT OF FUEL IN THE ST NO CHECK ND ELCE ECM YES DTC IS CUSED UNNI OUT OF FUEL 2003 COOLL MTIX (M940U) uthor : 400