In order to control emissions, a catalytic converter is used to convert harmful exhaust emissions into harmless water vapor and carbon dioxide.
The PCM has the capability to monitor this process by using a Rear Heated Oxygen Sensor (HO2S 2). The HO2S 2, located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst; this in turn indicates the catalyst's ability to convert exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front Oxygen Sensor (O2S 1).
If the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor assembly must be replaced. DO NOT attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the oxygen sensor wire(s). Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance. Refer to Diaf
grams, Heated Oxygen Sensor (O2S) Repair.
Conditions for Setting the DTC
DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441 not set.
Engine has been running longer than 30 seconds.
Engine Coolant Temperature (ECT) is greater than 4O C (1O4 F).
Calculated Air Flow is greater than 14 g/s for 140 seconds.
Throttle Position (TP) is between 5% and 56%.
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 fault active.
The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
A history DTC is stored.
Coolant fan turns ON.
Conditions for Clearing the MIL/DTC
The MIL will turn OFF after three 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.
DTC(s) can be cleared by using the scan tool.
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
Check for the following conditions:
Poor connection or damaged harness - Inspect PCM harness for open in CKT 1668. Check for the following conditions: Refer to Diagrams.
Poor terminal to wire connection
Intermittent test - Observe HO2S 2 on the scan tool while moving related connectors and wiring harness with the key ON. If the failure is induced, the HO2S 2 display will change. This may help isolate the location of the malfunction.
Number(s) below refer to the step number(s) on the Diagnostic Table.
The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.
This step determines if DTC P0140 is the result of a hard failure or an intermittent condition.
Disconnecting the HO2S 2 and jumpering CKT(s) 1668 and 1669 to ground will determine if the PCM or wiring or HO2S 2 is at fault.
Determines which circuit the fault is in. If CKT's 1668 and 1669 are OK, then the PCM connection or PCM is faulty.
Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.
Saturday, December 8th, 2012 AT 2:07 AM