Air Injection: Testing and Inspection

Chart C-6B - Air Management Check (PEDES) Valve (Part 1 of 2):

Wiring Diagram for Chart C-6B - Air Management Check (PEDES) Valve:

CHART C-6B - AIR MANAGEMENT CHECK (PEDES) VALVE (PART 1 OF 2)
(PRESSURE OPERATED ELECTRIC DIVERT/ELECTRIC SWITCHING

Circuit Description:


Air management is controlled by an air control and air switching valves, each with an ECM controlled vacuum solenoid. When the solenoid is grounded by the ECM, manifold vacuum will activate the valve and allow pump air to be directed as follows:

^ Air control solenoid not grounded by the ECM - Air diverted to silencer.

^ Air control solenoid grounded by the ECM - Air to air switching valve.

^ Air switching solenoid grounded by the ECM - Air to exhaust ports.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. This is a system functional check. Engine coolant temperature must be below 60°C (150°F). This step checks for air switching from port to converter. Since the air to the port time is very short on some engines, prepare to check for air to ports immediately after engine starts.

2. This will set a Code 42. When a code is set, the ECM opens the ground to the air control valve and allows air to divert. This checks for ECM response to a system fault.

3. This checks for a grounded circuit to the ECM. Test light "OFF" is normal and would indicate the circuit is not grounded.


4. Solenoids are "ON" or "OFF" by the ECM internal electronic switches called "drivers." Each driver is part of a group of four called quad-drivers. Failure of one can damage any other driver within the set. See CHART C-1.

Chart C-6B - Air Management Check (PEDES) Valve (Part 2 of 2):

CHART C-6B - AIR MANAGEMENT CHECK (PEDES) VALVE (PART 2 OF 2)
(PRESSURE OPERATED ELECTRIC DIVERT/ELECTRIC SWITCHING)

Test Description: Numbers below refer to circled numbers on the diagnostic chart.

5. Checks for an open in the solenoid control circuits. Grounding the test terminal should ground both solenoid circuits. Normally, the test light should be "ON" which indicates the problem is not in the ECM or wiring, but at the solenoid connections or valve itself.

6. Checks for open ignition circuit, grounding circuit shorted to 12V, or open ground wire. Only one terminal should light the test light.


7. Solenoids are turned "ON" or "OFF" by the ECM internal electronic switches called "drivers." Each driver is part of a group of four called quad-drivers. Failure of one can damage any other driver within the set. Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "driver." Using an ohmmeter, check the solenoid coil resistance ECM controlled relays and solenoids. See ECM wiring diagrams for coils to check and for pin identification.