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Diagnostic Circuit System Testing

  1. Turn ignition on. Check "GAUGE" fuse ("ECU-IG" on Camry and Supra, "WIPER" on Pickup and 4Runner, and "TURN GAG" on MR2). If fuse is blown, replace fuse and recheck system. If fuse blows again, check for short circuit between fuse and terminal No. 2 of main switch. Also inspect main switch.
  2. If fuse is okay, check for battery voltage between terminal No. 2 (terminal No. 16 on MR2 and RWD Corolla) of main switch and good body ground. If battery voltage is not present, check for open circuit between terminal and fuse.
  3. If voltage is present, unplug connector at main switch. Check for continuity between terminal No. 3 (terminal No. 4 on Cressida and Tercel, and terminal No. 20 on MR2 and RWD Corolla) of harness side of connector and good body ground. If continuity is not present, check for open circuit between terminal and body ground. Also check for faulty ground connection.
  4. If continuity is present, check for battery voltage between terminal No. 6 (terminal No. 5 on Cressida and Tercel, terminal No. 21 on MR2 and RWD Corolla) of harness side of connector and good body ground with main switch in "ON" position. If battery voltage is not present, check for short in harness between terminal of main switch and terminal No. 10 of cruise control computer. Also test main switch.
  5. If battery voltage is present, connect terminal No. 4 (terminal No. 1 on Cressida and Tercel, and terminal No. 18 on MR2 and RWD Corolla) of main switch to good body ground with main switch in "ON" position. If indicator light does not glow, test main switch.
    NOTE: Step 6) does not apply to MR2 and RWD Corolla. Go to Step 7).
  6. If indicator light glows, check for continuity between terminal No. 14 (terminal No. 2 on Celica and Supra) of control switch and good body ground. If continuity is not present, check for open circuit in harness between terminal and ground. Also test body ground circuit.
  7. If continuity is present, check for continuity between terminal No. 25 (terminal No. 3 on Celica and Supra, terminal No. 14 on MR2 and RWD Corolla, and terminal No. 24 on Pickup and 4Runner) of control switch and good body ground with "SET/COAST" in "ON" position.
  8. If continuity is not present, test control switch. If continuity is present, repeat step 7) with "SET/COAST" in "OFF" position. If continuity is present, check for short in harness between terminal and terminal No. 5 (terminal No. 17 on Celica and Supra).
  9. If continuity is not present, unplug electrical connector from cruise control computer. Check for battery voltage between harness connector terminal No. 10 and good body ground. If voltage is not present, check for open circuit in harness between terminal and terminal No. 6 (terminal No. 5 on Cressida and Tercel, and terminal No. 21 on MR2 and RWD Corolla) of main switch.
  10. If voltage is present, check for continuity between harness connector terminal No. 13 and good body ground. If continuity is not present, check for open circuit between terminal and ground. Also test body ground circuit.
  11. If voltage is present, connect harness connector terminal No. 3 to good body ground. If indicator light does not glow, check for open circuit in wire between terminal and terminal No. 4 (terminal No. 1 on Cressida and Tercel, terminal 18 on MR2 and RWD Corolla) of main switch.
  12. If indicator light glows, check for continuity between harness connector terminal No. 5 (terminal No. 17 on Celica and Supra) and good body ground with "SET/COAST" in "ON" position.
  13. If continuity is not present, check for open circuit in wire between terminal and terminal No. 25 (terminal No. 17 on Celica and Supra, and terminal No. 14 on MR2 and RWD Corolla, and terminal No. 24 on Pickup and 4Runner) of control switch. If continuity is present, replace cruise control computer.
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