Astro Van M V6-262 4.3L VIN W CPI (1992)
Intake Manifold Tuning Valve Circuit
Circuit Description:
The tuning valve is activated through a relay, by the ECM, during periods of acceleration where engine rpm is over 3000 and throttle position is
over 34%.
The tuning valve relay is powered by CKT 439 and turned "ON" and "OFF" when the ECM grounds CKT 1387. When the relay is activated, it
applies voltage from CKT 39 to CKT 1015, thus, opening the tuning valve.
Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if the system is functioning at the present time.
2. By cycling the tuning ON" and "OFF" will determine if the tuning valve relay is operating.
3. This will determine if the tuning valve relay has ignition voltage on CKT 39.
4. This will determine if the tuning valve relay has ignition voltage on CKT 439.
5. This step will determine if the relay related wiring to valve or the tuning valve is at fault.
6. This step will determine if the ECM, tuning valve relay or related wiring is at fault.
Diagnostic Aids:
TPS - An intermittent TPS output will cause the ECM to receive a false input.
