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Home / DTC / B1304 — Topstack POS.sensor:Up&Down=ON

B1304 — Topstack POS.sensor:Up&Down=ON

Detailed page for trouble code B1304.

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Code

B1304

MITSUBISHI B — Body

Topstack POS.sensor:Up&Down=ON

Brand: MITSUBISHI
Type: B — Body
Views: UK: 16 EN: 28 RU: 21
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Page language: EN

Causes

  • Short or cross-connection between the UP and DOWN sensor circuits
  • Failed/top stack position sensor with internal fault
  • Corroded, bent or loose connector pins
  • Damaged wiring harness (chafing, water ingress, pinched cable)
  • Faulty body control module (BCM) or input circuit

Symptoms

  • Convertible/top operation inhibited or behaves unpredictably
  • Warning lamp or message related to top/roof position
  • Top does not complete travel or stops unexpectedly
  • DTC stored and may immediately return after clear
  • Intermittent top operation or audible abnormal behavior from actuators

What to check

  • Read and record all stored codes and freeze-frame data with a scan tool
  • Verify that the code is repeatable: clear codes and operate the top to see if B1304 returns
  • Visually inspect sensor connector and wiring for damage, corrosion, or water entry
  • Check for continuity and shorts between UP and DOWN sensor wires with ignition OFF
  • Backprobe sensor connector during operation to observe UP and DOWN signal states
  • Inspect top mechanism alignment and limit switch actuator positions

Signal parameters

  • Normal: UP and DOWN signals should be mutually exclusive (only one active at a time)
  • Typical sensor behavior: ON = closed/grounded or ON = defined logic level; OFF = open/high impedance (verify vehicle-specific)
  • When both signals read active simultaneously: indicates short or sensor fault
  • Expected voltage ranges vary by model; measure with a multimeter or scope while operating the top

Diagnostic algorithm

  1. Use a diagnostic scan tool to confirm B1304 and any related codes. Note operating conditions when the code set occurred.
  2. Clear codes and attempt to operate the top/stack. Observe if B1304 returns and under what conditions (initial, during travel, when stopped).
  3. Perform a careful visual inspection of the top stack position sensor, its connector, and wiring harness, focusing on hinge areas where harness flexes.
  4. With ignition OFF, disconnect the sensor connector. Check for bent or pushed-out pins, corrosion, foreign debris, or water stains. Repair or replace connector if damaged.
  5. Check for continuity and shorts: measure resistance between UP and DOWN sensor terminals. They should not be shorted. Check each terminal to ground and to battery as appropriate per vehicle wiring.
  6. With ignition ON and backprobing connectors, operate the top while monitoring UP and DOWN signal lines with a multimeter or scope. Confirm signals are mutually exclusive; record readings.
  7. If wiring is intact but signals are incorrect, replace the top stack position sensor. Re-test to confirm correct operation and that code does not return.
  8. If replacement sensor does not fix the issue, trace wiring back to the BCM and check for shorts or intermittent faults. Repair wiring as required.
  9. If wiring and sensor are good but fault persists, inspect BCM input circuits and consider module programming or replacement following OEM procedures.
  10. After repairs, clear codes and perform multiple full open/close cycles to confirm repair stability.

Likely causes

  • Short to power or ground between UP and DOWN outputs at the sensor
  • Sensor internal contact welded or stuck delivering both outputs
  • Connector terminal corrosion allowing cross-contact
  • Harness damage near hinge or top mechanism causing intermittent shorts
  • Incorrect sensor alignment or mechanical interference causing both limit switches to trigger

Fault status

⚠️ Status
Top stack position sensor reports both UP and DOWN signals ON simultaneously. Indicates sensor or wiring fault; mutual exclusivity of limit switch signals violated.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

B1300 B1301 B1302 B1303 B1305 B1310
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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