Chart C-6A Secondary Air System Check - Belt Driven Pump

Chart C-6A:

Air Bypass Valve Circuit:

CIRCUIT DESCRIPTION
The secondary air injection bypass valve directs air into the exhaust ports or the atmosphere. Air is directed to the exhaust ports whenever the engine is started and the coolant temperature is above 20°C (68°F) and below 60°C (140°F) and system in "Open Loop," and engine speed below 1900 rpm. When the vehicle is started and the coolant temperature is below about 20°C (68°F), the air will be diverted to the atmosphere for the entire key cycle.

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

1. If the bypass valve does not have 34 kPa (10 inHg) of vacuum applied to it, check for a pinched, plugged or leak in the vacuum hose. The Engine Control Module (ECM) should energize the bypass valve at idle when coolant temperature is between 20°C (68°F) and 60°C (140°F) and system not in "Closed Loop." At high RPM between about 2000 - 2500 rpm, the ECM will de-energize the bypass valve which will divert air to the atmosphere.

2. Tests for a grounded bypass valve circuit. On a normal system, the light will be "OFF."

3. Checks for an open control circuit. Grounding diagnostic "test" terminal will energize the bypass valve if ECM and circuits are normal. In this step, if test light is "ON," circuits are normal and fault is in valve connection or valve.

DIAGNOSTIC AIDS
Removing diverter/silencer will allow easy access for determining if air is being diverted to atmosphere.