DTC Advanced Diagnostics: P0134
DTC P0134:Air/Fuel Ratio (A/F) Sensor (Sensor 1) Heater System Malfunction

General Description
The powertrain control module (PCM) monitors the air/fuel ratio (A/F) sensor (sensor 1) heater control circuit for malfunctions. The described tests will detect the following faults:
A/F sensor (sensor 1) heater heats too slowly from engine start (start check)
A/F sensor (sensor 1) below the temperature set point for an extended amount of time (permanent check)
A/F sensor (sensor 1) at very low temperature for a short time (low temperature check)

Internal heating is required when the heat transferred from the exhaust gas is not sufficient to maintain the A/F sensor (sensor 1) at its operating temperature. The required extra heating power depends on the deviation from the operating temperature. It can be controlled by varying the duty cycle.
Start check is only enabled if the start check enable conditions are met. Otherwise start check will be disabled for the current driving cycle. After moisture completely evaporated from exhaust pipe, if the system is normal, the sensor ceramic must reach a calibrated operating temperature within expected time. In case of the faults, such as sensor ageing, blackening of the protection tube, or transition resistances, it is no longer guaranteed that the sensor ceramic will reach its operating temperature. Start check monitors ceramic temperature against rationality threshold during the heating up. If after specified time, the sensor ceramic temperature still has not reached the target value, the PCM detects a malfunction and stores a DTC.
The permanent diagnosis monitors the ceramic temperature to check plausibility between the required heating output and the ceramic temperature. This diagnosis is continuously active if enable conditions are fulfilled. If the ceramic temperature drops below plausibility threshold, then the permanent check timer starts. If permanent check timer reaches its threshold, the PCM detects a malfunction and stores a DTC.
In addition to permanent diagnosis, the low temperature diagnosis monitors the ceramic temperature at a very low temperature. If the enable conditions are fulfilled, then it is continuously active. If the ceramic temperature quickly drops below a minimum plausibility threshold, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle*
Continuous**
Sequence
None
Duration
0.5 second or more
DTC Type
Two drive cycles, MIL on
*: Start check
**: Permanent diagnosis, low temperature diagnosis

Enable Conditions
Start check
Condition
Minimum
Maximum
Engine coolant temperature [ECT Sensor 1]
13.93 °F (-10.04 °C)
–
12 volt battery voltage [Battery]
–
16.1 V
State of the engine
Running
Other
A/F sensor (sensor 1) is active

Permanent diagnosis
Condition
Minimum
Maximum
Time not in fuel cut-off operation
5 seconds
–
Estimated exhaust gas temperature at A/F sensor (sensor 1)
391.93 °F (199.96 °C)
–
12 volt battery voltage [Battery]
–
16.1 V
Effective A/F sensor (sensor 1) heater voltage
10 V
–

Low temperature diagnosis
Condition
Minimum
Maximum
Time not in fuel cut-off operation
5 seconds
–
Estimated exhaust gas temperature at A/F sensor (sensor 1)
391.93 °F (199.96 °C)
–
[ ]: HDS Parameter

Malfunction Threshold
Any of the conditions is met:
Start check
The temperature of A/F sensor (sensor 1) heater ceramic does not reach 1,327.98 °F (719.99 °C) after 35 to 87 seconds the start check is executed.
Permanent diagnosis
The temperature of A/F sensor (sensor 1) heater ceramic is less than 1,327.98 °F (719.99 °C) for at least 60 seconds.
Low temperature diagnosis
The temperature of A/F sensor (sensor 1) heater ceramic is less than 1,184 °F (640 °C) for at least 10 seconds.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
A/F sensor (sensor 1) heater failure
A/F sensor (sensor 1) element failure

Confirmation Procedure
Operating Condition
Start the engine. Hold the engine speed [Engine Speed] at 3,000 rpm without load (in neutral) until the radiator fan comes on.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.