Chart A-1 Dwell Fixed Under 15 Degrees

Chart A-1:

Chart A-1 Wiring Diagram:

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Determines if the problem is CCC related or engine related. Dwell should start increasing as soon as engine is choked and go higher as it is choked more, until it goes over 50 degrees. With severe choking, the dwell could move up the scale momentarily even if it is not engine related, but it will move right back to a low dwell. If dwell responds the problem is a lean engine.

2. Checks for ECM response to input of 02 sensor circuit. The voltmeter is used to put a voltage on the oxygen sensor circuit to simulate a rich condition. Dwell should increase (a lean command) if ECM and harness are good.

3. Checks for normal coolant sensor circuit condition. Voltage on a normalized, hot engine should be under 2.5V.

4. This step checks for an open CKT 413 to ECM terminal "22" and grounded 02 sensor CKT 412. Terminal "5" voltage should be under 1.0 volt at idle. A high voltage could be caused by an open CKT 452 to terminal "22.

5. Checks for cause of lean condition that resulted in full rich command.