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Home / DTC / P0999 — Shift Solenoid F Control Circuit High

P0999 — Shift Solenoid F Control Circuit High

Detailed page for trouble code P0999.

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Code

P0999

Generic P — Powertrain

Shift Solenoid F Control Circuit High

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

Causes

  • Short to battery voltage in the shift solenoid F control wire
  • Faulty shift solenoid F (internal short or stuck)
  • Poor or corroded connector/pins at solenoid or TCM/ECM
  • Open or high-resistance ground or power circuits affecting control
  • Damaged wiring harness (pinched, chafed, melted)
  • Faulty TCM/ECM driver circuitry

Symptoms

  • Check Engine / Transmission warning lamp illuminated
  • Harsh, delayed, or no shifts; transmission may enter limp mode
  • Transmission stuck in one gear or limited gears
  • Stored transmission-related fault codes
  • Possible reduced fuel economy or abnormal shift behavior

What to check

  • Retrieve and record freeze frame data and all transmission-related DTCs
  • Visually inspect solenoid connector and wiring for damage, corrosion, or corrosion
  • Backprobe solenoid connector and monitor voltage while commanding solenoid ON and OFF
  • Measure solenoid coil resistance with harness disconnected
  • Check for continuity and shorts between control wire and battery positive, ground, and other circuits
  • Verify transmission power and ground circuits, fuses, and relays

Signal parameters

  • Control method: typically PWM from TCM/ECM; duty cycle varies with commanded pressure
  • Typical PWM frequency range (vehicle dependent): roughly 40–300 Hz
  • Expected coil resistance (varies by vehicle): commonly ~6–30 ohms — check OEM spec
  • Expected current draw (varies): roughly 0.3–2 A when energized
  • High-circuit symptom: measured voltage near battery voltage (~12 V) when the circuit should be pulled low

Diagnostic algorithm

  1. Connect a scan tool, record all codes and freeze-frame data. Confirm code P0999 is current and note conditions.
  2. Visually inspect the harness and connector at Shift Solenoid F and at the TCM/ECM for damage, corrosion, or loose pins.
  3. With ignition off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals; compare to OEM spec. Extremely low resistance suggests internal short.
  4. Check for short to battery: with harness disconnected, measure voltage between the control wire and ground with ignition ON; an unexpected battery voltage indicates a short to +12V in the harness.
  5. Backprobe the solenoid connector with the harness connected. Command the solenoid ON and OFF via the scan tool and observe voltage/ground behaviour. Note whether the module is switching the circuit and the voltage levels.
  6. Inspect power and ground circuits for the transmission control circuits (fuses, relays, ground straps). Repair any faults.
  7. Perform continuity test from the solenoid connector to the TCM/ECM pin to check for opens/high resistance or unintended shorts to other circuits.
  8. If wiring and connectors check OK, swap in a known-good identical solenoid (if available) and retest. If swapping cures the code, replace the solenoid.
  9. If replacement solenoid does not fix the issue and wiring is confirmed good, suspect TCM/ECM driver failure. Before replacing the TCM/ECM, re-verify wiring and consult manufacturer TSBs, and consider bench testing or module reprogramming as directed.
  10. Clear codes and perform a road test to confirm repair; monitor for recurrence and re-scan for related transmission faults.

Likely causes

  • Damaged harness with wire contacting +12V (short to battery)
  • Corroded or loose connector at the solenoid causing intermittent high reading
  • Failed solenoid coil with internal short
  • Faulty transmission control module driver (less common)

Fault status

⚠️ Status
Control module detects high voltage on Shift Solenoid F control circuit. Check wiring, connectors, solenoid resistance, and module driver. May cause transmission to enter limp mode; further diagnosis required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours (varies by vehicle and access to connectors)

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Code

P0999

LAND ROVER P — Powertrain

Solenoid control for shift F - high circuit

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

Causes

  • Short to battery voltage in the shift solenoid F control wire
  • Faulty shift solenoid F (internal short or stuck)
  • Poor or corroded connector/pins at solenoid or TCM/ECM
  • Open or high-resistance ground or power circuits affecting control
  • Damaged wiring harness (pinched, chafed, melted)
  • Faulty TCM/ECM driver circuitry

Symptoms

  • Check Engine / Transmission warning lamp illuminated
  • Harsh, delayed, or no shifts; transmission may enter limp mode
  • Transmission stuck in one gear or limited gears
  • Stored transmission-related fault codes
  • Possible reduced fuel economy or abnormal shift behavior

What to check

  • Retrieve and record freeze frame data and all transmission-related DTCs
  • Visually inspect solenoid connector and wiring for damage, corrosion, or corrosion
  • Backprobe solenoid connector and monitor voltage while commanding solenoid ON and OFF
  • Measure solenoid coil resistance with harness disconnected
  • Check for continuity and shorts between control wire and battery positive, ground, and other circuits
  • Verify transmission power and ground circuits, fuses, and relays

Signal parameters

  • Control method: typically PWM from TCM/ECM; duty cycle varies with commanded pressure
  • Typical PWM frequency range (vehicle dependent): roughly 40–300 Hz
  • Expected coil resistance (varies by vehicle): commonly ~6–30 ohms — check OEM spec
  • Expected current draw (varies): roughly 0.3–2 A when energized
  • High-circuit symptom: measured voltage near battery voltage (~12 V) when the circuit should be pulled low

Diagnostic algorithm

  1. Connect a scan tool, record all codes and freeze-frame data. Confirm code P0999 is current and note conditions.
  2. Visually inspect the harness and connector at Shift Solenoid F and at the TCM/ECM for damage, corrosion, or loose pins.
  3. With ignition off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals; compare to OEM spec. Extremely low resistance suggests internal short.
  4. Check for short to battery: with harness disconnected, measure voltage between the control wire and ground with ignition ON; an unexpected battery voltage indicates a short to +12V in the harness.
  5. Backprobe the solenoid connector with the harness connected. Command the solenoid ON and OFF via the scan tool and observe voltage/ground behaviour. Note whether the module is switching the circuit and the voltage levels.
  6. Inspect power and ground circuits for the transmission control circuits (fuses, relays, ground straps). Repair any faults.
  7. Perform continuity test from the solenoid connector to the TCM/ECM pin to check for opens/high resistance or unintended shorts to other circuits.
  8. If wiring and connectors check OK, swap in a known-good identical solenoid (if available) and retest. If swapping cures the code, replace the solenoid.
  9. If replacement solenoid does not fix the issue and wiring is confirmed good, suspect TCM/ECM driver failure. Before replacing the TCM/ECM, re-verify wiring and consult manufacturer TSBs, and consider bench testing or module reprogramming as directed.
  10. Clear codes and perform a road test to confirm repair; monitor for recurrence and re-scan for related transmission faults.

Likely causes

  • Damaged harness with wire contacting +12V (short to battery)
  • Corroded or loose connector at the solenoid causing intermittent high reading
  • Failed solenoid coil with internal short
  • Faulty transmission control module driver (less common)

Fault status

⚠️ Status
Control module detects high voltage on Shift Solenoid F control circuit. Check wiring, connectors, solenoid resistance, and module driver. May cause transmission to enter limp mode; further diagnosis required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours (varies by vehicle and access to connectors)

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P0750 P0751 P0753 P0756 P0760 P0765
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