OBD Guide
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P1821

Shift Fork Position Sensor 1 System Voltage High Range Out

P1821 is an OBD-II diagnostic trouble code meaning: Shift Fork Position Sensor 1 System Voltage High Range Out. Common causes: shift fork position sensor malfunction, short circuit in the sensor circuit. Estimated repair cost: $33–167.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$33–167 (est.)

Symptoms

  • Gear shifting problems
  • Hard or abrupt shifts
  • Transmission transition to emergency mode
  • Check Engine Light Illuminates
  • Reduced transmission efficiency

Causes

  • Shift fork position sensor malfunction
  • Short circuit in the sensor circuit
  • Wiring harness damage
  • Problems with the sensor power supply
  • Transmission control module (TCM) malfunction

How to Fix

  1. Check the integrity of the sensor circuit
  2. Check resistance and sensor signal
  3. Scan all associated trouble codes
  4. If necessary, replace the fork position sensor
  5. Check and update TCM firmware if necessary

Related codes

P1820P1822P1823

FAQ

What does the P1821 code mean?

P1821 is an OBD-II diagnostic trouble code that indicates: Shift Fork Position Sensor 1 System Voltage High Range Out

What causes a P1821 error code?

The most common causes of P1821 include: Shift fork position sensor malfunction; Short circuit in the sensor circuit; Wiring harness damage; Problems with the sensor power supply.

How do I fix a P1821 diagnostic trouble code?

To fix P1821: Check the integrity of the sensor circuit. Check resistance and sensor signal. Scan all associated trouble codes. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1821?

Yes, but get it checked soon

How much does it cost to fix P1821?

The estimated repair cost for P1821 is $33–167. Actual cost depends on your vehicle, location, and labor rates.

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