P2237
3MZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2237: Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)
DTC P2237 - Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)
DTC P2238 - Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1)
DTC P2239 - Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 1 Sensor 1)
DTC P2240 - Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 2 Sensor 1)
DTC P2241 - Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 2 Sensor 1)
DTC P2242 - Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 2 Sensor 1)
DTC P2252 - Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 1 Sensor 1)
DTC P2253 - Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 1 Sensor 1)
DTC P2255 - Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 2 Sensor 1)
DTC P2256 - Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 2 Sensor 1)
DESCRIPTION
HINT:
- Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
The A/F sensor generates voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM (Included in HV control ECU) with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.
The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.
A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NOx) into less harmful substances. To allow the TWC to function effectively, it is necessary to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio.
*: Value changes inside the ECM (Included in HV control ECU). Since the A/F sensor is the current output element, a current is converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.
HINT:
- DTCs P2237, P2238, P2239, P2252 and PP2253 indicate malfunctions related to the bank 1 A/F sensor circuit.
- DTCs P2240, P2241, P2242, P2255 and PP2256 indicate malfunctions related to the bank 2 A/F sensor circuit.
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that includes cylinder No. 2.
MONITOR DESCRIPTION
The Air-Fuel Ratio (A/F) sensor varies its output voltage in proportion to the air-fuel ratio. If the A/F sensor impedance (alternating current resistance) or output voltage deviates greatly from the standard range, the ECM (Included in HV control ECU) determines that there is an open or short in the A/F sensor circuit.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
P2237 and P2240 (Open circuit between AF+ and AF-):
P2238 and P2241 (Admittance low):
Except P2237, P2240 (Open circuit between AF+ and AF-) and P2238, P2241 (Admittance low):
TYPICAL MALFUNCTION THRESHOLDS
P2237 and P2240 (Open circuit between AF+ and AF-):
P2238 and P2241 (Admittance low):
P2238 and P2241 (Short circuit between AF+ and GND):
P2238 and P2241 (Short circuit between AF+ and AF-):
P2239 and P2242 (Short circuit between AF+ and +B):
P2252 and P2255 (Short circuit between AF- and GND):
P2253 and P2256 (Short circuit between AF- and +B):
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT: Techstream only:
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using Techstream.
1 Connect Techstream to the DLC3.
2 Put the engine in inspection mode Inspection Mode Procedure.
3 Start the engine and turn the tester ON.
4 Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
5 On the tester, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
6 Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
7 Monitor the output voltages of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.
HINT:
- The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
Standard:
NOTE: The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.
- Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.
- To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 or AFS B2 S1 and O2S B1 S2 or O2S B2 S2 then press the graph button on the Data List view.
HINT:
- Read freeze frame data using Techstream. The ECM (Included in HV control ECU) records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was LEAN or RICH, and other data from the time the malfunction occurred.
PROCEDURE
1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
(a) Disconnect the A3 or A4 A/F sensor connector.
(b) Measure the resistance between the terminals of the A/F sensor connector.
Standard resistance:
(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
2. INSPECT A/F RELAY
(a) Remove the A/F relay from the engine room R/B.
(b) Measure the A/F relay resistance.
Standard resistance:
(c) Reinstall the A/F relay.
NG -- REPLACE A/F RELAY
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - HV CONTROL ECU)
(a) Disconnect the A3 and A4 A/F sensor connectors.
(b) Turn the ignition switch to the ON position.
(c) Measure the voltage between the +B terminal of the A/F sensor connector and body ground.
Standard voltage:
(d) Turn the ignition switch off.
(e) Disconnect the H33 HV control ECU connector.
(f) Check the resistance.
Standard resistance (Check for open):
Standard resistance (Check for short):
(g) Reconnect the HV control ECU connector.
(h) Reconnect the A/F sensor connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE HV CONTROL ECU