Troubleshooting
DTC P0134 Insufficient Temp. for Closed Loop Fuel ControlCIRCUIT DESCRIPTION
DTC Detecting Condition:
HINT: The ECM provides a pulse width modulated control circuit to adjust current through the heater. The A/F ratio sensor heater circuit uses a relay on the B+ side of the circuit.
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 the 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 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 ECM of the LEAN condition (small electromotive force: < 0.45 V).
When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas in reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive force: > 0.45 V).
The ECM 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 ECM is unable to perform accurate air-fuel ratio control. The oxygen sensors include a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temp. of the exhaust gas is low) current flows to the heater to heat the sensor for accurate oxygen concentration detection.
HINT:
After confirming DTC P0134, use the OBD II scan tool or hand-held tester to confirm voltage output of oxygen sensor (bank 1 sensor 1) from "CURRENT DATA".
If voltage output of oxygen sensor (bank 1 sensor 1) is less than 0.1 V, oxygen sensor (bank 1 sensor 1) circuit may be open or short.
Wiring Diagram:
Step 1:
Step 2 - 5:
Step 6 - 10:
Step 11 - 12:
INSPECTION PROCEDURE
HINT:
- If the vehicle run out of fuel, the air-fuel ratio is LEAN and DTC P0134 will be recorded. The MIL then comes on.
- Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame 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 warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.
CHECK FOR INTERMITTENT PROBLEMS
HINT:
HAND-HELD TESTER only:
By putting the vehicle's ECM in check mode, 1 trip detection logic is possible instead of 2 trip detection logic and the sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
a. Clear the DTC.
b. Set the check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Handle the connector.
CONFIRMATION DRIVING PATTERN
1. Connect the hand-held tester to the DLC3.
2. Switch the hand-held tester from "normal mode" to "check mode".
3. Start the engine and let the engine idle for 100 sec. or more.
4. Drive the vehicle at 40 km/h (24 mph) or more for 20 sec. or more.
5. Let the engine idle for 20 sec. or more.
6. Let the engine idle for 30 sec.
HINT: If a malfunction exists, the MIL will light up during step (6).
NOTE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a hand-held tester, turn the ignition switch OFF after performing steps (3) to (6), then perform steps (3) to (6) again.