P0157

: DTC P0157; LEFT-HAND CATALYST MONITOR SENSOR SENSING CIRCUIT LOW/HIGH VOLTAGE, NO ACTIVITY

G258127t49 : CHECK THE CATALYST MONITOR SENSOR SENSING CIRCUIT FOR HIGH RESISTANCE
1. Disconnect the battery negative terminal.
2. Disconnect the catalyst monitor sensor electrical connector, PI13.
3. Disconnect the ECM electrical connector, PI01.
4. Measure the resistance between PI13, pin 04 (N) and PI01, pin 129 (N).

- Is the resistance greater than 5 ohms?

-> Yes
REPAIR the high resistance circuit. CLEAR the DTC. TEST the system for normal operation.

-> No

G258127t50 : CHECK THE CATALYST MONITOR SENSOR SENSING CIRCUIT FOR SHORT TO HIGH VOLTAGE
1. Reconnect the battery negative terminal.
2. Turn the ignition switch to the ON position.
3. Measure the voltage between PI13, pin 04 (N) and GROUND.

- Is the voltage greater than 3 volts?

-> Yes
REPAIR the short circuit to high voltage. CLEAR the DTC. TEST the system for normal operation.

-> No

G258127t51 : CHECK THE CATALYST MONITOR SENSOR SENSING CIRCUIT FOR SHORT TO GROUND
1. Turn the ignition switch to the OFF position.
2. Measure the resistance between PI13, pin 04 (N) and GROUND.

- Is the resistance less than 10,000 ohms?

-> Yes
REPAIR the short circuit to GROUND. CLEAR the DTC. TEST the system for normal operation.

-> No

G258127t52 : CHECK THE CATALYST MONITOR SENSOR GROUND CIRCUIT FOR OPEN CIRCUIT
1. Measure the resistance between PI13, pin 03 (B) and PI01, pin 130 (BW).

- Is the resistance greater than 5 ohms?

-> Yes
REPAIR the circuit. CLEAR the DTC. TEST the system for normal operation.

-> No
INSTALL a new catalyst monitor sensor. CLEAR the DTC. TEST the system for normal operation.