Air Injection Pump - Runs After Every Engine Start

18-34

Air Injection Pump - Runs After Every Engine Start - Normal Operation - Revised Control

MODEL:
93 MY 4.0L Engines

DATE:
7/93

Beginning with the 1993 model year, the air injection pump on 4.OL engines will run for a period of time after every engine start. The pump is switched off by the engine management ECM after a programmed number of engine revolutions. This number will vary and is dependant on coolant temperature. The pump is also switched off if engine speed exceeds 2500 RPM.

Oxygen sensor feedback is enabled just before the air injection pump is switched off. It is normal for the feedback voltage to indicate excess air in the exhaust when the air pump running. This will NOT flag a diagnostic trouble code.

NOTE:
The air pump on previous model year 3.6L and 4.0L engines operates only when coolant temperature is between 60° F and 120° F.