LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jeep >> 1981 >> Pickup J20, AWD >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Exhaust Gas RECIRCULATION >> Testing >> CTO Switch
April 5, 2026: LEMON Manuals is launched! Read the announcement.

CTO Switch

NOTE: Engine coolant temperature must be below 100°F to perform this test.
  1. Check vacuum lines for leaks and correct routing. Disconnect vacuum line at back-pressure sensor (if equipped) or at EGR valve, and attach this line to a vacuum gauge.
  2. Operate engine at 1500 RPM. No vacuum should be indicated on gauge. If vacuum is shown, replace CTO switch.
  3. Idle engine until coolant temperature exceeds 100°F on 4 cylinder engines, or 115°F on 6 and 8 cylinder engines.
  4. Accelerate engine to 1500 RPM. Carburetor ported vacuum should be shown on gauge. If not, replace CTO switch.
scientia non olet · About LEMON Manuals