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Home / DTC / P1605 — Transmission Control Module Checksum Error

P1605 — Transmission Control Module Checksum Error

Detailed page for trouble code P1605.

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Code

P1605

LAND ROVER P — Powertrain

Transmission Control Module Checksum Error

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Corrupted or interrupted TCM software/firmware update
  • Failed or degraded TCM internal memory (EEPROM/FLASH)
  • Low or unstable battery/charging system voltage during write operations
  • Poor power/ground connections to the TCM
  • Damaged wiring or connectors (corrosion, broken wires, water ingress)
  • CAN/vehicle network communication errors between TCM and other control modules

Symptoms

  • Transmission fault lamp or MIL illuminated
  • Transmission in limp-home mode or reduced gear range
  • Erratic, harsh or missing shifts
  • Failure to engage drive or reverse in some cases
  • Stored fault codes related to transmission and communication

What to check

  • Read and record all stored DTCs and freeze-frame data with a capable scan tool
  • Check battery state of charge and charging system voltage (engine running ~13.5–14.8 V; key on engine off >= 12.4 V)
  • Inspect TCM connectors and harness for corrosion, bent pins, water ingress, or physical damage
  • Verify good power and ground at the TCM with wiring diagrams
  • Check CAN/LIN bus continuity and voltage levels (idle bus voltages near specified mid-levels on differential signals)
  • Attempt communication with the TCM using dealer-level or OEM diagnostic tool (verify module is responding and reportable software/calibration IDs)

Signal parameters

  • Battery voltage (Key On Engine Off >=12.4 V; Running 13.5–14.8 V)
  • TCM supply voltage and ground circuit integrity
  • CAN bus activity and error counters (should show normal traffic, no bus-off)
  • TCM UDS/diagnostic response and software part/calibration numbers
  • TCM internal status or checksum/validation flags when available via OEM tool

Diagnostic algorithm

  1. Connect a capable OEM or dealer-level scan tool. Read and record all DTCs, freeze frame, and module information (software and calibration IDs).
  2. Verify battery charge and charging system voltage. Recharge or load-test battery if voltage is low; ensure stable power during diagnostics and programming.
  3. Visually inspect TCM connector and harness for damage, corrosion, or water ingress. Repair or replace damaged wiring and connectors as needed.
  4. Verify power and ground at the TCM pins with a multimeter; repair any faults. Re-check for related intermittent faults after repairs.
  5. Confirm CAN/vehicle network communication to the TCM. Repair any network wiring issues or terminate problems. Clear codes and re-scan.
  6. If hardware and communications are good, attempt to read TCM software/calibration ID. If the module reports incorrect or missing calibration, try a controlled reflash/reprogram of the TCM using OEM software and a fully charged battery with stable power.
  7. If programming fails repeatedly or the TCM shows persistent checksum/memory errors after a successful reflash attempt, suspect internal module failure. Replace TCM with a correct part and program VIN/calibrations per manufacturer procedures.
  8. After repair or reflash, clear DTCs, perform required relearns or adaptions, road test to verify normal shifting and that the code does not return.
  9. If code returns after replacement, investigate related modules and vehicle network for faults that could corrupt TCM memory (for example intermittent power or communication interruptions).

Likely causes

  • Interrupted or failed TCM reflash/programming
  • Corroded connector or poor power/ground to the TCM
  • Internal TCM memory failure
  • Low battery voltage during previous programming or drive cycle

Fault status

⚠️ Status
Manufacturer-specific code: TCM checksum/memory integrity failure detected. The transmission control module has failed its internal checksum validation and flagged a memory/firmware integrity error. Module may require reprogramming or replacement.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-4.0 hours

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413

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