High Altitude Switch
- Locate the high altitude switch under driver's seat. Disconnect the altitude switch plug. Connect an ohmmeter to switch terminals. The altitude switch should be open under 3300 ft. (1000 m).
- Warm engine to operating temperature. Disconnect the oxygen sensor. Disconnect the high altitude switch. Remove vacuum hose from the fuel pressure regulator and plug.
- Connect an exhaust gas analyzer to the exhaust pipe. Operate engine at 2000 RPM and note CO% level.
- Bridge the high altitude switch harness terminals. At 2000 RPM, CO% level should be leaner. If not, check high altitude connectors. Ensure continuity of one wire to ground. The other wire should have continuity to CU terminal 28.