1986 Mercury Lynx Base, MTXIIFACTORY OEM SERVICE PROCEDURE

Test Y - Canister Purge (CANP) Check

  1. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO and positive test lead to positive battery terminal. Using a jumper wire, connect STI circuit to signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of CONTINUOUS SELF-TEST codes (DVOM reads zero volts). Depress and release throttle, DVOM should change to a high voltage reading. If reading did not change, depress throttle to WOT and release. If STO voltage does not go high, go to TEST NN - NO CODES/CODES NOT LISTED , step 17). Leave test equipment hooked up. If reading changed, remain in OUTPUT STATE CHECK and go to next step.
  2. Set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR on CANP solenoid and negative test lead to CANP output circuit on solenoid. Depress and release throttle several times to cycle solenoid on and off. If CANP solenoid does not cycle, remove jumper wire and go to step 4). If CANP solenoid does cycle, go to next step.
  3. Turn key off and wait 10 seconds. Remove jumper wire from STI to signal return. Disconnect vacuum hose from CANP solenoid on PCV side. Apply 16 in. Hg vacuum to solenoid. If CANP solenoid does not hold vacuum, replace it and repeat QUICK TEST . If code 42 is still displayed, service fuel evaporation system. If CANP holds vacuum, EEC-IV is okay. Check fuel system.
  4. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector. Measure solenoid resistance. If reading is less than 40 ohms or more than 90 ohms, replace CANP solenoid and repeat QUICK TEST . If reading is between 40 and 90 ohms, connect solenoid and go to next step.
  5. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between VPWR at CANP harness connector and ground. If reading is less than 10.5-volts, repair open circuit and repeat QUICK TEST . If reading is 10.5-volts or more, go to next step.
  6. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between CANP signal at connector and test pin 35. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST . If reading is less than 5 ohms, go to next step.
  7. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect CANP solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between test pins 40, 46, 60 and test pin 35. If any reading is less than 10,000 ohms, repair short to power and repeat QUICK TEST . If any reading is 10,000 ohms or more, go to next step.
  8. Turn key off and wait 10 seconds. Leave CANP solenoid disconnected. Leave breakout box installed and ECA disconnected. Measure resistance between test pins 37, 57 and test pin 35. If any reading is less than 10,000 ohms, repair short to ground and repeat QUICK TEST . If code is repeated, replace ECA. Repeat QUICK TEST . If any reading is 10,000 ohms or more, remove breakout box. Replace ECA and repeat QUICK TEST .
Fig 1: Canister Purge (CANP) Circuit
G4280
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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