OBD Guide
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P18BB

Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range

P18BB is an OBD-II diagnostic trouble code meaning: Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range. Common causes: malfunction of the internal mode switch, open or short circuit in the circuit. Estimated repair cost: $17–56.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$17–56 (est.)

Symptoms

  • Incorrect gear shifting
  • Check Engine light comes on
  • The car may go into emergency mode
  • Problems determining the current transmission mode
  • Reduced vehicle dynamics

Causes

  • Malfunction of the internal mode switch
  • Open or short circuit in the circuit
  • Poor contact in connectors
  • Problems with the transmission control unit
  • Contact corrosion

How to Fix

  1. Check the integrity of wiring and connectors
  2. Test the operation of the mode switch
  3. Check the voltage in the circuit
  4. Replace the faulty switch if necessary
  5. Reset the error and check the system operation

Related codes

P18BAP18BCP18BD

FAQ

What does the P18BB code mean?

P18BB is an OBD-II diagnostic trouble code that indicates: Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range

What causes a P18BB error code?

The most common causes of P18BB include: Malfunction of the internal mode switch; Open or short circuit in the circuit; Poor contact in connectors; Problems with the transmission control unit.

How do I fix a P18BB diagnostic trouble code?

To fix P18BB: Check the integrity of wiring and connectors. Test the operation of the mode switch. Check the voltage in the circuit. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P18BB?

Limited driving only, diagnose soon

How much does it cost to fix P18BB?

The estimated repair cost for P18BB is $17–56. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat