Code
P1634
LINCOLN
P — Powertrain
Data Output Link Circuit Failure
Views:
UK: 19
EN: 41
RU: 35
AI status
Completed
Completed
100%
Causes
- Damaged or corroded connector or pin at PCM or a related module
- Open, short to ground, or short to battery in the data link wiring
- Failed PCM or other control module driver circuit
- Blown fuse or faulty power/ground supplying the module
- Poor chassis or engine ground
- Water intrusion or physical damage to harness
Symptoms
- MIL (Check Engine) lamp illuminated
- Loss or intermittent loss of communication with one or more modules (error messages on scanner)
- Inoperative or erratic instrument cluster functions, warning lights, or network-controlled features
- Possible drivability symptoms if affected module controls engine components
- DTC present persists after battery disconnect/clear if fault is permanent
What to check
- Retrieve all stored/active/permanent codes and freeze frame using a capable scan tool
- Verify battery voltage and charging system (11–14.5 V with engine off/running)
- Inspect module connectors and wiring for corrosion, bent pins, water intrusion, or physical damage
- Check fuses and relays that supply the affected module(s)
- Backprobe and measure data line and module supply/ground voltages
- Wiggle harnesses and connectors while monitoring for changes in data/communication
Signal parameters
- Module supply voltage: approximately 11–14.5 V (vehicle dependent)
- Ground continuity: near 0 Ω; voltage drop to chassis ground typically
- CAN bus idle voltages (if applicable): CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V
- LIN bus idle voltage (single-wire networks): typically near battery voltage via pull-up (approx. 9–14 V depending on ignition state)
- Data line resistance to other nodes: expected low resistance when connected (verify against service data)
- No short to battery or ground on data line (infinite/very high resistance expected to supply rails)
Diagnostic algorithm
- Confirm the code and record freeze-frame and any related U-codes using a scan tool.
- Verify battery voltage and health. Low voltage can cause communication faults.
- Visually inspect connectors and wiring at the PCM and any modules on the same data link (look for corrosion, bent pins, water, chafing).
- Check fuses and relays for module power and replace if blown. Verify module ignition feed and constant power where applicable.
- Backprobe the module power, ground, and data output pin. Compare measured voltages with expected signal parameters.
- Check continuity and resistance of the suspect data/output wire to other network nodes and to module connectors. Repair any open or high-resistance connections.
- Wiggle-test harnesses/connectors while monitoring the scan tool for changes. If intermittent, use a scope or data-logger to capture events.
- If data line is shorted to battery/ground, isolate by unplugging connectors and testing segments to locate short; repair wiring or replace damaged connector.
- If wiring and power/ground check OK, consider module driver failure. Reflash or replace the suspect module only after confirming wiring integrity.
- Clear codes and perform full functional test / road test. Re-scan to ensure code does not return.
Likely causes
- Connector corrosion or bent pins at the PCM/data module
- Single-wire network (LIN) shorted to battery or ground
- PCM internal output transistor/driver failure
- Missing or weak ground at module
- Blown module power fuse or ignition feed
- Damaged wiring where harness flexes (doors, firewall, engine areas)
Fault status
Status
Data Output Link Circuit Failure — The vehicle detected an electrical/communication fault on a data output or serial network circuit. Check wiring, connectors, module power/ground, and module driver for faults.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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