P1921 Transmission range signal out of range or implausible (Ford)

Transmission range signal (Ford)

Severity not verified — if the car runs badly, have it inspected

Ford owners report sudden downshifts and rear-wheel lockup at speed with this code, but we found no Ford statement on whether it is safe to keep driving.

Source: how we rate severity

P1921 in short

On Ford, P1921 means the transmission range signal, which tells the computer which gear position is selected, is out of range or implausible. Ford dealers have traced it to the range sensor or its molded lead frame, usually alongside P0706, P0707 and P1702. Owners report sudden downshifts; get it checked promptly.

The transmission range sensor tells the computer whether the lever is in park, reverse, neutral or drive. On Ford, P1921 sets when that signal is out of range or does not make sense.

Ford dealers quoted in owner complaints usually found it with P0706, P0707 and P1702 on 2015–2017 F-150s with the 6R80 and a 2016 Transit, and traced it to the range sensor or the molded lead frame inside the transmission.

Owners describe the wrench light, a blank gear display, unexpected downshifts at highway speed and in some cases the rear wheels locking. A separate Ford recall covers unexpected downshifts on the 2014 F-150 from a speed sensor signal; it does not name this code.

Pick your make

P1921 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Molded lead frame or range sensor fault inside the transmission

    Supported by vehicle data
    Why it ranks here
    Ford dealers quoted in several F-150 complaints confirmed a faulty molded lead frame or range sensor with P1921.
    What would change this
    Rises if P0706, P0707 or P1702 are stored too, or wiggling the shifter reproduces the fault.

  2. Range sensor wiring or connector fault

    Possible — needs testing
    Why it ranks here
    Range sensor circuit codes often come with P1921, so the wiring is checked before replacing internal parts.
    What would change this
    Rises if the connector is damaged or corroded.

  3. Speed sensor signal loss covered by the 2014 F-150 recall

    Possible — needs testing
    Why it ranks here
    Recall 24V-444 covers unexpected downshifts on the 2014 F-150 from loss of the output speed sensor signal; it does not name P1921, so treat it as context only.
    What would change this
    Rises only on a 2014 F-150 with the recall still open.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read codes from the engine and transmission modules with a scan tool that supports both, before anything is cleared.

    Low riskTool: scan tool that reads the transmission module

  2. Check for open recalls on your VIN at nhtsa.gov/recalls or with a Ford dealer.

    Low risk

  3. Have a shop watch the range sensor reading while moving the shifter and check the circuit.

    Best left to a shopTool: scan tool with live transmission data

    Warning:Shop test. On many Ford transmissions the lead frame is inside the transmission.

Symptoms

  • Wrench and check engine lights
  • Gear position display blank or flashing
  • Unexpected downshift at speed
  • Transmission stuck in one gear (limp-home mode)
  • Rear wheels briefly locking while driving

How to fix

  1. Do not clear the code before the transmission module has been read.

  2. Check your VIN for open recalls and have the range sensor checked promptly by a shop or Ford dealer.

Parts and cost context

  • Transmission control module (TCM):On F-150s the lead frame that carries the range sensor is often replaced with or near the main control; the transmission computer is not the usual fix.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2015–2017 · F-150

    Supported by vehicle data

    Owners report Ford dealers finding P1921 with P0706, P0707 and P1702 on the 6R80 and replacing the range sensor or molded lead frame after sudden downshifts or limp mode.

  • 2016 · Transit

    Supported by vehicle data

    An owner quotes a Ford dealer diagnosis of P1921 transmission range signal with range sensor codes, traced to the range sensor or lead frame.

  • P0706Transmission range sensor signal out of range or not plausible

    Shares causes Supported by vehicle data

    P0706 (range sensor circuit range/performance) appears with P1921 in most Ford dealer readouts.

  • P0707Transmission range sensor circuit signal too low

    Shares causes Supported by vehicle data

    P0707 (range sensor circuit low) appears with P1921 in most Ford dealer readouts.

All Transmission codes

Sources and review

  1. NHTSA complaint ODI 11476584: 2015 Ford F-150 dealer diagnosis — NHTSA Office of Defects Investigation
  2. NHTSA complaint ODI 11650215: 2016 Ford F-150 dealer diagnosis — NHTSA Office of Defects Investigation
  3. NHTSA complaint ODI 11475327: 2016 Ford F-150 dealer diagnosis — NHTSA Office of Defects Investigation
  4. NHTSA complaint ODI 11573118: 2016 Ford Transit dealer diagnosis — NHTSA Office of Defects Investigation
  5. NHTSA Recall 24V-444 (Ford 24S37): unexpected downshift to first gear, 2014 F-150 — Ford Motor Company / NHTSA (via vehiclesafetyrecalls.com)
  6. NHTSA complaint ODI 11458070: 2017 Ford F-150 code readout — NHTSA Office of Defects Investigation
  7. Scan data code P1921 — TAT (Transmission and Auto Technology) scandata code list
Last reviewed
Written by
Saurabh K.
Editorial review
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Technician review
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