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HOMESERVICE MANUALSFORD1991AEROSTAR VAN CARGO EXTENDED, 4.0 X, AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTSDIS SYSTEM (2.3L RANGER)PINPOINT TEST C
1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWD

Pinpoint Test C

1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWDSECTION Pinpoint Test C
  1. Check For Left Side Spark With KOER  Start engine and using spark tester, check for spark at each left spark plug wire. If spark is present at any left spark plug wire, go to step 2). If spark is not present, go to PINPOINT TEST D, Step 1).
  2. Check IDM With KOER  With key off, install DIS diagnostic cable module tee (pin Nos. 7-12) to DIS module. Connect DIS diagnostic cable to BOB. Use 2.3L DP DIS overlay. Connect LED test light positive lead to IDM (J4) and negative lead to BAT (J60). Start engine and observe test light. If test light blinks continuously, go to step 3). If test light does not blink, go to step 4).
  3. Check IDM To ECA Continuity To ECA  With key off, disconnect ECA. Crank engine and observe test light. If test light blinks continuously, replace ECA. ECA does not respond to IDM input. Remove test equipment and reconnect all components. Clear Continuous Memory Codes and rerun Quick Test. If test light does not blink, go to step 4).
  4. Isolate ECA & Check IDM Circuit During Cranking  With key off, disconnect ECA. Crank engine and observe test light. If test light blinks continuously, replace ECA. The ECA is shorting IDM. If test light does not blink, go to step 5).
  5. Check IDM For Short To Power  With key off, and disconnect HEGO sensor. Disconnect DIS diagnostic cable module tee (pin Nos. 7-12) from DIS module. Set DVOM on 20-k/ohm scale. Measure resistance between IDM (J4) and VBATD (J5). If resistance is less than 10 k/ohms, check connectors and service or replace harness. IDM is shorted to VBAT. Remove test equipment and reconnect all components. Clear Continuous Memory Codes and rerun Quick Test. If resistance is 10 k/ohms or more, go to step 6).
  6. Check IDM For Short To Ground  With key off and disconnect diagnostic cable connector from DIS module (pin Nos. 7-12). Set DVOM on 20-k/ohm scale. Measure resistance between IDM (J4) and BAT (J60). If resistance is 10 k/ohm or less, check connectors and service or replace harness. IDM is shorted to ground. Remove test equipment and reconnect all components. Clear Continuous Memory Codes and rerun Quick Test. If resistance is 10 k/ohm or more, replace DIS module. IDM is shorted in DIS module. Remove test equipment and reconnect all components. Clear Continuous Memory Codes and rerun Quick Test.
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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.