Description
DATA TROUBLE CODE: 29SYSTEM: Sub Heated Oxygen Sensor Circuit (Right)
CIRCUIT DESCRIPTION
To obtain a high purification rate for the Co, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the engine control module of the LEAN condition (small electromotive force: 0 Volt).
When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the engine control module of the RICH condition (large electromotive force: 1 Volt).
The engine control module judges by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the engine control module is unable to perform accurate air-fuel ratio control.
The main heated oxygen sensors include a heater which heats the Zirconia element. The heater is controlled by the engine control module. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the heater to heat the sensor for accurate oxygen concentration detection.
DIAGNOSTIC TROUBLE CODE DETECTING CONDITION
- Open or short in heater circuit of sub heated oxygen sensor for 0.5 seconds or more.
OR
- Main heated oxygen sensor signal is 0.45 volts or more and sub heated oxygen sensor signal is 0.45 volts or less under the following conditions: (2 trip detection logic)
- Engine coolant temperature 80°C (176°F) or more.
- Accelerator pedal fully depressed for 2 seconds or more.
TROUBLE AREA
- Open or short in heater circuit of sub heated oxygen sensor.
- Sub heated oxygen sensor.
- engine control module.
OR
- Open or short in sub heated oxygen sensor circuit.
- Sub heated oxygen sensor.
- engine control module.
HINT: Diagnostic trouble code 27 is for the left bank sub heated oxygen sensor circuit. Diagnostic trouble code 29 is for the right bank sub heated oxygen sensor circuit.
DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose Of The Driving Pattern
To simulate Diagnostic Trouble Code detecting condition after Diagnostic Trouble Code is recorded. To check that the malfunction is corrected when the repair is completed confirming that Diagnostic Trouble Code is no longer detected.
Detection Driving Pattern
Malfunction: open or short in Sub Heated Oxygen Sensor.
1. Disconnect the EFI fuse (20 A) for 10 seconds or more, with Ignition switch OFF. Initiate test mode (Connect terminal TE2 and E1 of Data Link Connector 1 with Ignition switch OFF).
2. Start the engine and warm up with all ACC switch OFF.
3. After the engine is warmed up, let it drive at 50 to 55 mph for 10 minutes or more.
4. After driving, stop at a safe place and perform idling for 2 minutes or less.
5. After performing the idling in step 4, perform acceleration to 60 mph with the throttle valve fully open.
NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible. If a malfunction exists, the Malfunction Indicator Lamp will light up during step 5.
Malfunction Indicator Lamp
Normal Mode On
Test Mode On