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P1634

Data Output Link Circuit Failure.

  • Mercury
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
6
AreaComputer and output circuits
34
FaultThe specific fault in that area

What it means

P1634 on a Mercury means Data Output Link Circuit Failure, the same definition Ford uses for this code. The engine control module (PCM) monitors the communication link it uses to send data to other modules and has detected a fault in that circuit. Exact wording and the modules involved vary by model and year, so check the manufacturer's information for the specific vehicle.

Symptoms

  • Warning lights on, such as the check engine light
  • Other warning lights or gauges behaving oddly, if modules cannot receive data
  • Instrument cluster readings missing or erratic
  • Poor or inconsistent communication with the diagnostic scan tool
  • Possible drivability complaints, depending on which modules rely on the data
  • Possible intermittent fault that comes and goes

Possible causes

  • Damaged, chafed or corroded wiring in the data link circuit between the PCM and other moduleslikely
  • Loose, corroded or water-damaged connector at the PCM or a connected modulelikely
  • Faulty or poorly grounded connected module pulling the data link down or interfering with itpossible
  • Low battery voltage or poor power or earth supply to the PCM or other modulespossible
  • Internal fault in the PCM affecting its data outputrare
  • Previous aftermarket electrical work or accessories interfering with the data circuitrare

How to diagnose

  1. Read all stored and pending codes from every module and note any communication or voltage codes alongside P1634
  2. Record freeze frame data and check whether the fault is current or intermittent after clearing and retesting
  3. Check battery condition and charging voltage, as low or unstable voltage can upset module communication
  4. Visually inspect wiring and connectors for the data circuit at the PCM and connected modules for chafing, corrosion, water ingress or pin damage
  5. Check power and earth supplies to the PCM, including fuses and earth points, against the wiring diagram
  6. Wiggle-test the harness while monitoring live data or communication to find intermittent faults
  7. Test the data link circuit for continuity, short to earth and short to voltage using the wiring diagram for the specific model
  8. Disconnect connected modules one at a time, if the manufacturer's procedure allows, to see if one is loading the circuit

How to fix

  • Repair or replace damaged wiring in the data link circuit
  • Clean, repair or replace corroded or damaged connectors and terminals
  • Restore good power and earth connections, and fix any battery or charging problem
  • Replace a faulty connected module that is disturbing the data link, after confirming with testing
  • Replace or reprogram the PCM only after wiring, connectors and supplies are proven good and the manufacturer's procedure calls for it

Can I keep driving?

Medium severity

The car can usually be driven short-term if it runs normally, but get it checked soon as communication faults can affect other systems and may get worse. If drivability worsens or safety-related warning lights appear, stop driving and seek help.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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