P0140
DTC P0140 HO2S CKT Insufficient Activity Sensor2
Circuit Description
The HO2S 2, located in the exhaust stream past the catalytic converter, produces an output signal relative to the oxygen storage capacity of the catalytic converter. The PCM can then determine the ability of the catalytic converter to convert the exhaust emissions effectively. The HO2S 2 signal will be far less active than the signal produced by the front Oxygen Sensor 1 (O2S 1).
Conditions for Running the DTC
- DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 not set.
- Air flow is greater than 5.5 grams per second.
- Engine Coolant Temperature (ECT) is greater than 40 °C (104 °F).
- Throttle Position (TP) is between 4% and 56%.
Conditions For Setting The DTC
HO2S 2 remains between 425 mV and 460 mV for 125 seconds.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present.
- The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
- A history DTC stores.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault
- A history DTC will clear after 40 consecutive warm up cycles without a fault
- A scan tool can clear the DTCs
Diagnostic Aids
Whenever the oxygen sensor pigtail wiring, the connector, or the terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, the rear HO2S 2 must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade the performance of the oxygen sensor.
A poor connection, rubbed through wire insulation or a wire broken inside the insulation may cause an intermittent.
Check for the following conditions:
- A poor connection or damaged harness - Inspect the PCM harness for the following condition:
- Open in the rear HO2S high circuit
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wire connection
- Damaged harness.
- An intermittent test - Observe the rear HO2S 2 on the scan tool while moving the related connectors and wiring harness with the key ON. Whenever the fault is induced, the rear HO2S 2 display will change. This may help isolate the location of the malfunction.
Steps 1 - 2:
Steps 3 - 5:
Steps 6 - 10:
Steps 11 - 12:
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
2. This step determines if DTC P0140 is the result of a hard malfunction or an intermittent condition.
4. Disconnecting the HO2S 2 and connecting a jumper wire between the HO2S 2 signal circuit and the HO2S 2 low circuit to ground, will determine if the PCM or wiring or HO2S 2 is malfunctioning.
6. This step determines which circuit the malfunction is in. If the HO2S 2 signal circuit and the HO2S 2 low circuit are OK, this is an indication that the PCM electrical connection or the PCM is malfunctioning.
10. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu technical Communications System (ITCS) information for PCM programming and CKP System Variation Learn Procedure for the crankshaft position system variation learn procedure.