Chart A-2 Dwell Fixed Between 10 and 50 Degrees

- Chart A-2 Dwell Fixed Between 10 and 50 Degrees.:

- Wiring Diagram for Chart A-2 Dwell Fixed Between 10 and 50 Degrees.:

CHART A-2, DWELL FIXED BETWEEN 10° AND 50°

OPEN COOLANT OR OXYGEN SENSOR CIRCUIT

CHART DESCRIPTION
1. Running engine at part throttle for one minute warms up the oxygen sensor.
Grounding O2 sensor input checks ECM response to a "lean" signal.
Normal response-dwell decreases to full rich command.
1a. On some ECM's, an open in circuit to Term. "14"can cause open loop.
1b. Checks output of O2 sensor with full rich command from ECM caused by grounded O2 sensor input.
Normal response, voltage at O2 sensor over .8 volt.
2. This step grounds O2 sensor circuit at ECM to check for opens in wiring, to ECM Terminals "9" and "14".
Normal response to "lean" signal, dwell decreases; that is a rich command.
3. This step checks for voltage to the coolant sensor.
Normal reading on a warm engine is less than 2.5 volts.
An open circuit would cause a reading of approximately 5 volts.