OBD Oxygen Sensor P0130, P0135
This follows the investigation of two oxygen sensor related fault codes.
The original oxygen sensor had a fault code P0130 (bank 1 sensor 1 oxygen circuit). The suspect faulty OEM oxygen sensor was replaced with a pattern part, and a new error code P0135 (bank 1 sensor 1 oxygen heater circuit fault) followed.
The original oxygen sensor had a fault code P0130 (bank 1 sensor 1 oxygen circuit). The suspect faulty OEM oxygen sensor was replaced with a pattern part, and a new error code P0135 (bank 1 sensor 1 oxygen heater circuit fault) followed.
Hardware Checks
Measuring the resistance of the new heater element read 15 ohms.
The wiring loom was resistance checked and probed, no shorts to ground found, and no open circuits.
The heater element 12v supply comes via an ecu fuse through an ignition switch relay to the heater. The ground side of the circuit is transistor switched to ground in the ECU.
Putting a scope on the ECU liaded switching side, shows a 20% duty cycle on startup. After a few minutes, warmup it switches to 100% duty (heater fully on). I assume this gradual phasing happens, to protect the element from blowing from a cold shock start.
So all looks good on the surrounding circuitry side.
However, the resistance of the original heating element shows 5 ohms.
Ohms law on the original 5 ohm, gives a current of 12/5=2.4 amps
On the new 15 ohm, it gives 12/15=0.8 amps.
The toyota online repair manual at "tcorolla.net" states it should be 5 to 10 ohms.
My hunch is that this is the cause of the P0135.
The wiring loom was resistance checked and probed, no shorts to ground found, and no open circuits.
The heater element 12v supply comes via an ecu fuse through an ignition switch relay to the heater. The ground side of the circuit is transistor switched to ground in the ECU.
Putting a scope on the ECU liaded switching side, shows a 20% duty cycle on startup. After a few minutes, warmup it switches to 100% duty (heater fully on). I assume this gradual phasing happens, to protect the element from blowing from a cold shock start.
So all looks good on the surrounding circuitry side.
However, the resistance of the original heating element shows 5 ohms.
Ohms law on the original 5 ohm, gives a current of 12/5=2.4 amps
On the new 15 ohm, it gives 12/15=0.8 amps.
The toyota online repair manual at "tcorolla.net" states it should be 5 to 10 ohms.
My hunch is that this is the cause of the P0135.
Mode 6 Data?
The p0135 dtc usually comes on during a short journey. So I suspect its one of the non continuous tests triggered on a particular driving pattern.eg 5 mins idle then 25mph speed.
So trying to reproduce this fault by revving the engine whilst stationary will not trigger the fault code.
Looking at the mode 6 emission test showed the heater circuit test fault. Sometimes it would show as passed, so was borderline.
The tcorolla website shows the mode 6 parameters at the bottom as TEST ID $04 and COMPONENT TEST IDs $81 and $82. Unfortunately these didnt return any data on my ELM327 terminal session (commands 060481, 060482).
Howevet my engine code 4ZZ does not match the 1ZZ engine this site refers to. Normally it would show min, max and actual values for the current in the heater circuit.
Users could use dedicated manufacturer specific diagnostic software to review these test results. However, i am wary of adding another chinese clone to the pile. Especially with this car being 20 years old and not supporting CAN bus.
So trying to reproduce this fault by revving the engine whilst stationary will not trigger the fault code.
Looking at the mode 6 emission test showed the heater circuit test fault. Sometimes it would show as passed, so was borderline.
The tcorolla website shows the mode 6 parameters at the bottom as TEST ID $04 and COMPONENT TEST IDs $81 and $82. Unfortunately these didnt return any data on my ELM327 terminal session (commands 060481, 060482).
Howevet my engine code 4ZZ does not match the 1ZZ engine this site refers to. Normally it would show min, max and actual values for the current in the heater circuit.
Users could use dedicated manufacturer specific diagnostic software to review these test results. However, i am wary of adding another chinese clone to the pile. Especially with this car being 20 years old and not supporting CAN bus.
Swap It Back
I suspected the first trouble code was actually raised by a faulty coil pack on its way out, which was subsequently replaced.
So I swapped back in the original oxygen sensor.
The fault was cleared and has not reappeared.
So be wary of pattern parts and check the resistance of the heater coil before swapping it out.
So I swapped back in the original oxygen sensor.
The fault was cleared and has not reappeared.
So be wary of pattern parts and check the resistance of the heater coil before swapping it out.