P0999

Code

LAND ROVER P — Powertrain

Solenoid control for shift F - high circuit

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 23 EN: 35 RU: 30

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Page language: EN

Causes

Open or intermittent wiring in the solenoid F high-side circuit
Short to battery (voltage) on the solenoid F control wire
Poor or corroded connector/pin at the solenoid or TCM
Failed shift solenoid F (coil shorted or open)
Faulty TCM/transmission control driver output
Poor ground or supply voltage problem

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Transmission may go into limp/reduced-gear mode
Harsh, delayed or missing shifts associated with the gear controlled by solenoid F
Stored and repeating transmission-related DTCs
Erratic shift behavior or inability to shift into specific gear(s)

What to check

Read and record all stored and pending DTCs and freeze-frame data
Check transmission fluid level and temperature (safe operating range) before extended testing
Visually inspect wiring harness and connectors at transmission and TCM for damage, corrosion, or loose pins
Back-probe solenoid connector while commanding solenoid (live data/bi-directional test)
Measure coil resistance of solenoid F with harness disconnected
Check for proper battery voltage at the circuit supply and good ground(s)

Signal parameters

Typical solenoid coil resistance (approximate): 10–40 Ω (varies by design) — compare to manufacturer spec
When commanded ON (depending on design): driver pulls to ground or switches to battery. Expect near battery voltage on supply (≈11–14 V) and switching at the driver output or near 0 V when activated — consult vehicle-specific wiring diagram
If PWM-controlled: duty cycle range 0–100% and frequency commonly 50–200 Hz (vehicle-specific)
Open-circuit expected: infinite Ω; short-to-battery: near 0 Ω to battery voltage on control wire when uncommanded — verify against wiring diagram

Diagnostic algorithm

Safety first: apply parking brake, chock wheels, and work on a cool transmission. Use proper PPE.
Scan: Read codes and freeze-frame data. Note related transmission codes and MIL history.
Visual: Inspect wiring and connectors at solenoid F and TCM for corrosion, bent pins, chafing, or heat damage.
Supply/Ground: With ignition ON, measure battery voltage at the transmission harness power supply and verify engine/chassis grounds are clean and tight.
Resistance: With harness disconnected, measure solenoid F coil resistance and compare to spec. Replace solenoid if out of range or open/shorted.
Command test: Using a scan tool, command solenoid F while back-probing the control wire. Observe voltage behavior (switching to ground or battery as designed) and any PWM signal. Note deviations.
Wiggle/intermittent: With solenoid commanded, wiggle harness and connectors for intermittent changes in signal or codes.
Isolation: If wiring suspect, unplug connector at TCM and check continuity/resistance between TCM pin and solenoid pin; repair opens/shorts. If necessary, use a jumper harness of known good condition to test.
Controller: If wiring and solenoid test good and the TCM output does not switch correctly, suspect a TCM/driver failure — verify with manufacturer service info before replacing.
Post-repair: Clear codes, perform road/test cycle and re-scan to confirm repair. Verify proper shift operation.

Likely causes

Open or high-resistance connector/wiring to solenoid F
Corroded or bent terminal at solenoid or TCM connector
Failed solenoid coil
Short to battery on the control wire
Faulty TCM output stage

Fault status

⚠️ Status

Transmission shift solenoid F control circuit — high/incorrect voltage detected. Check wiring, connector, solenoid, and TCM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.8-2.5 hours

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P0999 — Solenoid control for shift F - high circuit