2UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM

Transcription

1 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM 89 P0037 Oxygen Sensor Heater Control Circuit Low (ank Sensor ) P0038 Oxygen Sensor Heater Control Circuit High (ank Sensor ) P0057 Oxygen Sensor Heater Control Circuit Low (ank Sensor ) P0058 P04 Oxygen Sensor Heater Control Circuit High (ank Sensor ) Oxygen Sensor Heater Circuit Malfunction (ank Sensor ) P06 Oxygen Sensor Heater Circuit Malfunction (ank Sensor ) DCRIPTION Sensor refers to the sensor mounted behind the Three-Way Catalyst Converter (TWC) and located far from the engine assembly. In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric air fuel level. For the purpose of helping the ECM to deliver accurate air fuel ratio control, a Heated Oxygen (HO) sensor is used. The HO sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low). When the air fuel ratio becomes lean, the oxygen concentration in the exhaust gas is rich. The HO sensor informs the ECM that the post-twc air fuel ratio is lean (low voltage, i.e. less than 0.45 V). Conversely, when the air fuel ratio is richer than the stoichiometric air fuel level, the oxygen concentration in the exhaust gas becomes lean. The HO sensor has the property of changing its output voltage drastically when the air fuel ratio is close to the stoichiometric level. The ECM uses the supplementary information from the HO sensor to determine whether the air fuel ratio after the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the HO sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air fuel ratio control.

2 90 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM Atmosphere Air Housing Platinum Electrode Ideal Air Fuel Mixture Output Voltage Solid Electrolyte (Zirconia Element) Heater Cover Coating (Ceramic) Richer - Air Fuel Ratio - Leaner Exhaust Gas A5539E0 The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The heated oxygen sensor heater circuit uses a relay on the + side of the circuit. Reference (System Diagram of ank Sensor ) EFI Heated Oxygen Sensor ECM From attery EFI Fuse EFI No. Fuse Heater HT Sensor OX Duty Control E MREL Ground A3784E04 No. Detection Condition Trouble Area P0037 P0057 Heater current is 0.5 A or less when the heater operates with more than 0.5 V positive battery voltage Open in Heated Oxygen (HO) sensor heater circuit Heated Oxygen (HO) sensor heater EFI Relay ECM

3 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM 9 No. Detection Condition Trouble Area P0038 P0058 P04 P06 When heater operates, heater current exceeds.0 A ( trip detection logic) Cumulative heater resistance correction value exceeds threshold ( trip detection logic) ank refers to the bank that includes No. cylinder. ank refers to the bank that does not include No. cylinder. Sensor refers to the sensor closest to the engine assembly. Sensor refers to the sensor farthest away from the engine assembly. Short in HO sensor heater circuit HO sensor heater EFI Relay ECM Open or short in HO sensor heater circuit HO sensor heater EFI relay ECM MONITOR DCRIPTION The sensing portion of the Heated Oxygen (HO) sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the difference between the oxygen concentration surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor. Heated oxygen sensor heater range check (P0037, P0038, P0057 and P0058): The ECM monitors the current applied to the O sensor heater to check the heater for malfunctions. If the current is below the threshold value, the ECM determines that there is an open circuit in the heater. If the current is above the threshold value, the ECM determines that there is a short circuit in the heater. The ECM constantly monitors the current applied to the heater. IF the ECM detects an open or short circuit, the ECM turns the MIL on and sets a. If a malfunction is detected, the ECM cuts off the current applied to the heater. Example: The ECM sets P0038 or P0058 when the current in the HO sensor heater is more than A. Conversely, when the heater current is less than 0.3 A, P0037 or P0057 is set. Heated oxygen sensor heater performance (P04 and P06): After the accumulated heater ON time exceeds 00 seconds, the ECM calculates the heater resistance using the battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM determines that there is a malfunction in the HO sensor heater and sets P04 or P06. MONITOR STRATEGY Related s Required sensors / components Required sensors / components Frequency of operation Duration MIL operation P0037: Heated oxygen sensor heater (bank ) range check (low current) P0038: Heated oxygen sensor heater (bank ) range check (high current) P0057: Heated oxygen sensor heater (bank ) range check (low current) P0058: Heated oxygen sensor heater (bank ) range check (high current) P04: Heated oxygen sensor heater performance (bank ) P06: Heated oxygen sensor heater performance (bank ) Heated oxygen sensor heater Vehicle speed sensor (VSS) Continuous: P0037, P0038, P0057 and P0058 Once per driving cycle: P04 and P06 second: P0037, P0038, P0057 and P seconds: P04 and P06 Immediate: P0037, P0038, P0057 and P0058 driving cycle: P04 and P06

4 9 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM Sequence of operation None TYPICAL ENALING CONDITIONS All: The monitor will run whenever these s are not present None P0037 and P0057 (Low current): duration of the following conditions are met: 0.5 seconds or more (a) Time after heaters are OFF second or more (b) Following conditions are met - attery voltage 0.5 V or more to less than 0 V Learned heater current during heater OFF Completed Intrusive heating Heater is OFF Less than 0. seconds Heater current Less than 0.3 A P0038 and P0058 (High current): When one of following conditions is met: Condition (a), (b) or (c) (a) When all conditions are met: - attery voltage 0.5 V or more Engine Running Starter OFF Catalyst monitoring active A/F control Active heater OFF control Active heater ON control (b) When all conditions below are met: - attery voltage 0.5 V or more to less than 0 V Learned heater current during heater OFF Completed Active heater OFF control Active heater On control Heater OFF time Less than 0. seconds Heater current A or more (c) Heater OFF time second or more P04 and P06 attery voltage Fuel cut Time after fuel cut ON to OFF Accumulated heater ON time Learned heater current during heater OFF 0.5 V or more OFF 30 seconds or more 00 seconds or more Completed TYPICAL MALFUNCTION THRHOLDS P0037 and P0057 (Low current): Heater current - Learned heater OFF current Less than 0.3 A P0038 and P0058 (High current): When either condition below is met: Condition A or A. Learned heater OFF current More than A. Heater current - Learned heater OFF current 5 A or more P04 and P06 Heater resistance Varies with sensor element temperature (example: More than 3 Ω)

5 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM 93 COMPONENT OPERATING RANGE HOS heater current 0.4 to A (at idle, warmed-up engine and +: to 4 V) MONITOR RULT Refer to CHECKING MONITOR STATUS (See page -7). WIRING DIAGRAM Engine Room R/ ECM W- L EFI Relay 5 3 Engine Room R/ W-G 35 IC4 W-G H8 Heated Oxygen Sensor (ank Sensor ) 8 E8 MREL J J3 W- J/C EFI No. L-W J8 J4 J/C J/C 7 L-W L-W L-W IC3 IM A A C EFI Engine Room R/ D C C D L-W L-W L-W + R HT R E OX 4 3 H6 Heated Oxygen Sensor (ank Sensor ) + HT R E OX 4 3 E E W P (Shielded) G-Y (Shielded) E J8 J/C W- W- 5 E5 33 E5 E4 8 E4 8 E4 E6 HT OX HT OX E E E attery ED EE A38E0

6 94 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM INSPECTION PROCEDURE Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction. INSPECT HEATED OXYGEN SENSOR (HEATER RISTANCE) Component Side HO Sensor (a) (b) Disconnect the H6 or H8 Heated Oxygen (HO) sensor connector. Measure the resistance of the HO sensor connector. Standard resistance Tester Connection H6 H8 + HT (c) NG HT () - + () HT () - E (4) Reconnect the HO sensor connectors. to 6 Ω at 0 C (68 F) 0 kω or higher REPLACE HEATED OXYGEN SENSOR E OX A3788E0 OK INSPECT EFI RELAY (a) (b) Remove the EFI relay from the engine room relay block. Measure the resistance of the EFI relay. Standard resistance Terminal Connection kω or higher 3-5 elow Ω (when battery voltage applied to terminals and ) 0600E03 (c) Reinstall the EFI relay. NG REPLACE EFI RELAY OK

7 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM 95 3 INSPECT ECM (HT OR HT VOLTAGE) E4 E5 ECM Connector (a) (b) Turn the ignition switch ON. Measure the voltage of the E4 and E5 ECM connectors. Standard voltage Terminal Connection HT (E4-) - ody ground HT (E5-5) - ody ground 9 to 4 V HT HT E845E The HT means the heated oxygen sensor bank sensor. The HT means the heated oxygen sensor bank sensor. OK REPLACE ECM NG

8 96 UZ-FE ENGINE CONTROL SYSTEM SFI SYSTEM 4 CHECK HARNS AND CONNECTOR (HEATED OXYGEN SENSOR - EFI RELAY, HEATED OXYGEN SENSOR - ECM) Wire Harness Side: Heated Oxygen Sensor Connector (a) (b) (c) (d) Turn the ignition switch OFF. Disconnect the H6 or H8 oxygen sensor connectors. Disconnect the E4 and E5 ECM connectors. Measure the resistance. Standard resistance (Check for open) H6 ank H8 ank + HT Front View E4 E5 HT HT ECM Connector Engine Room R/: (e) (f) Terminal Connection HT (H6-) - HT (E4-) HT (H8-) - HT (E5-5) Standard resistance (Check for short) Terminal Connection HT (H6-) or HT (E4-) - ody ground HT (H8-) or HT (E5-5) - ody ground Remove EFI relay from engine room R/. Measure the resistance. Standard resistance (Check for open) Tester Connection + (H6-) - EFI relay (3) + (H8-) - EFI relay (3) Standard resistance (Check for short) elow Ω elow Ω 0 kω or higher 0 kω or higher elow Ω Tester Connection + (H6-) or EFI relay (3) - ody ground + (H8-) or EFI relay (3) - ody ground 0 kω or higher EFI Relay A3789E0 (g) (h) (i) Reconnect the ECM connectors. Reconnect the oxygen sensor connectors. Reinstall the EFI relay. NG REPAIR OR REPLACE HARNS OR CONNECTOR OK REPLACE ECM