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Home / DTC / B1578 — PS.cut SW SHT.to GND for COM

B1578 — PS.cut SW SHT.to GND for COM

Detailed page for trouble code B1578.

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Code

B1578

MITSUBISHI B — Body

PS.cut SW SHT.to GND for COM

Brand: MITSUBISHI
Type: B — Body
AI status
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ready
Completed 100%
Page language: EN

Causes

  • Chafed or damaged wiring harness with conductor contacting chassis ground
  • Corroded, bent or pushed‑out connector pin shorting to ground
  • Water intrusion or contamination in connector causing short
  • Failed power steering cut switch or internal short in the switch
  • Faulty body/control module or internal short in the module
  • Aftermarket device or improper repair created a splice to ground

Symptoms

  • DTC B1578 stored and possible related communication faults
  • Power steering cut function may be disabled or behave abnormally
  • Steering assistance reduced or intermittently lost
  • Instrument panel warning lamp for power steering or body control
  • Other modules reporting communication/malformed input from switch

What to check

  • Read and record all stored codes and freeze‑frame/live data with a diagnostic scanner
  • Visually inspect wiring and connectors at the power steering cut switch and along the harness routing (steering column, dash bulkhead)
  • Look for rubbed through insulation, pinched wires, or corrosion and signs of moisture
  • Disconnect the PS cut switch connector and see if the code clears or changes
  • Backprobe the COM/signal pin with a multimeter to measure voltage with ignition ON and while operating the switch
  • With ignition OFF, check continuity from the COM pin to chassis ground (should not be continuous)

Signal parameters

  • Expected: COM/signal line typically at a reference voltage (commonly ~5 V) with ignition ON and switch in inactive position
  • Fault condition: voltage near 0 V (ground) when shorted to chassis ground
  • Normal continuity: high resistance/open circuit between signal pin and chassis ground (no continuity)
  • When switch actuated (if applicable): change in voltage or resistance per wiring diagram (logic level change)
  • Use manufacturer wiring diagram for exact pin location and expected voltages

Diagnostic algorithm

  1. Connect scan tool, record codes and live data related to power steering and body/control modules.
  2. Visually inspect harness, connectors and repair history around the steering column and bulkhead. Repair obvious damage.
  3. With ignition OFF, unplug the PS cut switch connector. Check continuity between the COM pin on the harness side and chassis ground. If continuity present, trace and repair short in harness.
  4. With connector disconnected, measure resistance/shorts between COM pin and other nearby circuits to find chafed wires or pin contact.
  5. With connector plugged, backprobe the COM/signal pin with ignition ON and measure voltage. Compare to expected reference voltage. Operate switch while observing change. If voltage is ~0 V and should be high, there is a short to ground.
  6. Perform a wiggle test on harness and connectors while monitoring voltage/live data to locate intermittent grounding point.
  7. If harness and connector test good, swap or bench test the PS cut switch (if removable/replaceable) or substitute known-good module per factory procedure.
  8. If wiring and switch are good, suspect control module fault. Verify with wiring diagram and consult manufacturer procedures before replacing module; consider reflashing software where applicable.
  9. After repair, clear codes, perform functional test/road test and re-scan to confirm code does not return.

Likely causes

  • Wiring short to chassis ground at or near the steering column
  • Connector terminal pushed out/corroded at the switch harness
  • Failed PS cut switch
  • Intermittent grounding from water/contamination in connector
  • Less likely: internal fault in the control module

Fault status

⚠️ Status
Power Steering cut switch COM/communication circuit shorted to ground detected by control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1577 B1579 B1580
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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