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LS400 Theft Deterrent Ignition Switch Circuit Test

  1. Turn ignition off. Check 15-amp ECU-IG and CIG fuses. ECU-IG and CIG fuses are located in junction block No. 1 in lower left side of dash. If a fuse is bad, go to next step. If fuses are okay, go to step 3).
  2. If a fuse is bad, repair short in wire harness or components between related fuse and theft deterrent ECU terminals A2 (ECU-IG) and B7 (CIG). See Figure. Theft deterrent ECU is located under left side of dash, above junction block No. 1.
  3. Disconnect theft deterrent ECU connectors. Turn ignition switch to ON position. Using a DVOM, check for battery voltage between theft deterrent ECU harness terminals A2 and B7 and body ground. See Figure.
  4. If battery voltage is not present, repair open circuit in wire harness between harness terminals A2 and B7 and battery. If battery voltage is present, replace theft deterrent ECU, and retest system.
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