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Home >> Suzuki >> 1999 >> Grand Vitara JS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1408: Manifold Differential Pressure (MDP) Sensor Circuit Malfunction >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

  1. Remove PCM cover, located below right side of instrument panel. Connect DVOM (backprobe) between PCM 26-pin connector "B" terminals No. 13 (Red/White wire) and No. 20 (Gray/Yellow wire). Turn ignition on. Reading should be 4.0-5.0 volts. Start and idle engine. Reading should be 1.2-2.0 volts. If voltage readings are not as specified, go to next step. If voltage readings are as specified, check for intermittent problem. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If all checks are okay, replace PCM. See REMOVAL, OVERHAUL & INSTALLATION article. Retest system.
  2. Turn ignition off. Disconnect 3-pin Manifold Differential Pressure (MDP) sensor harness connector, located on top of engine near right side valve cover. Turn ignition on. Using DVOM, measure voltage between MDP sensor harness connector terminals No. 2 (Gray/Yellow wire) and No. 3 (Gray/Red wire). If 4.5-5.5 volts exists, go to next step. If 4.5-5.5 volts does not exist, go to step  4 .
  3. Check for open or short in Red/White wire between PCM and MDP sensor. See WIRING DIAGRAMS article. If Red/White wire is okay, replace MDP sensor. See REMOVAL, OVERHAUL & INSTALLATION article. Retest system.
  4. Check for open or short in Gray/Red wire or Gray/Yellow wire between PCM and MDP sensor. See WIRING DIAGRAMS article. If Gray/Red wire and Gray/Yellow wire are okay, replace PCM. See REMOVAL, OVERHAUL & INSTALLATION article. Retest system.
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