Code
P1831
Other
P — Powertrain
Transmission Transfer Case Counter Clockwise Shift Relay Coil Short Circuit To Ground
Views:
UK: 29
EN: 42
RU: 46
AI status
Completed
Completed
100%
Causes
- Relay coil internal short
- Damaged/ chafed wiring between TCM and relay (shorted to chassis ground)
- Corroded or damaged relay connector pins making unintended ground
- Faulty relay socket or mounting point grounding the circuit
- Failed TCM/PCM driver transistor (internal short to ground)
- Water intrusion or debris causing a short in connector or splice
Symptoms
- Transfer case will not shift to or from the CCW shift position
- Illumination of 4WD/transfer case warning lamp or MIL
- Intermittent or no response when selecting 4WD modes
- Stored DTC P1831 and possibly related transmission/transfer case codes
- Possible blown fuse for transfer case control circuits
- Burnt smell or visible heat damage at relay/connector in severe shorts
What to check
- Retrieve and record freeze‑frame and all related DTCs with a scan tool
- Visually inspect relay, relay socket, connector and wiring for corrosion, damage, melting or water intrusion
- Check related fuses and fusible links for open/blown condition
- With ignition off disconnect the relay and inspect pins for corrosion or shorting to ground
- Use an ohmmeter to measure coil resistance of relay (compare to known good relay or manufacturer spec)
- With ignition on and relay disconnected, backprobe the TCM/PCM relay driver pin to check for unintended ground (use DMM/oscilloscope)
Signal parameters
- Battery voltage: ~12 V (engine off) to ~13.5–14.5 V (engine running) present to relay feed terminal when circuit powered
- Relay coil resistance: within manufacturer specification (typical automotive relay coils commonly range from about 5 Ω to several hundred ohms — check service data)
- Control signal: TCM driver should be open/high when relay is off and switch to ground or low to energize coil (verify with scan tool or scope)
- Measured continuity: control driver to ground should be open when relay and system are off; short to ground indicates fault
Diagnostic algorithm
- Read and record all stored codes and freeze frame data. Check for related transfer case or transmission codes. 2) Visually inspect the relay, relay socket, wiring harness and nearby ground points for damage, corrosion or signs of burning. Repair obvious damage. 3) Inspect and test fuses for the transfer case control circuits. Replace any blown fuses and note if they immediately blow again. 4) With ignition off, remove the CCW shift relay. Inspect relay pins and socket for corrosion or a foreign conductive path. 5) Measure the relay coil resistance on a known good relay and compare to the suspect relay; replace the relay if coil reads out of spec or shows near‑zero resistance. 6) With the relay removed, use a digital multimeter to check the control (driver) wire resistance to chassis ground and look for a short to ground. There should be high resistance/OL when circuit is intact. 7) Backprobe the relay control wire at the connector with ignition on and try to command the CCW shift with a scan tool while monitoring the control circuit voltage. Verify whether the TCM is commanding and whether the line is being held to ground incorrectly. 8) If the wiring is open/short-free and relay is good but fault persists, suspect a control module driver fault — consult manufacturer service information before replacing the module. 9) After repairs, clear codes and perform functional test of transfer case shifting and confirm no reoccurrence of the code.
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Likely causes
- Damaged harness where it passes near body/chassis causing insulation wear and contact with ground
- Corroded connector at the relay or transfer case shift assembly allowing a ground path
- Failed relay with internal coil short
- Control module output driver failed (less common than wiring/relay failure)
Fault status
Status
Transfer case CCW shift relay coil circuit has a short to ground. The control module detected the relay driver line grounded or low resistance to chassis ground; relay, wiring, connector or module driver may be defective.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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