P278B — Kick Down Switch Circuit Range/Performance

OBD2 code P278B flags a problem with the sensor and actuator circuits (kick down switch circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, poor ground connection, corroded, loose or damaged connector.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P278B is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the kick down switch for damage, corrosion, chafing or poor contact.
Subsystem check Compare the kick down switch live reading against a known-good reference (specification or a correlated sensor) under the conditions from the freeze frame.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P278B does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P278B (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250. Overall, fixing P278B usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P278B?

Drivers most often notice: the affected system operates intermittently or not at all, possible limp mode depending on the affected component, Check Engine Light on, increased fuel consumption in some cases.

Is it safe to drive with P278B?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How do I diagnose P278B myself?

Start with a scan: confirm P278B, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the kick down switch, and verify the suspect component against live data before buying parts.

What is the most common cause of P278B?

The most common causes are: control module driver fault, poor ground connection, corroded, loose or damaged connector.

What does OBD2 code P278B mean?

What does P278B mean?

The engine control module sets P278B when it detects a fault in the sensor and actuator circuits. In practical terms: kick down switch circuit range/performance. The code belongs to the powertrain (engine/transmission) group of OBD2 codes.

“Range/performance” means the signal from the kick down switch is electrically valid but does not match what the module expects for current operating conditions. The wiring is usually intact; the problem is a degraded component, a drifted sensor or a mechanical fault upstream.

This code does not appear from a single bad reading: the module must see the fault condition repeat under defined operating conditions before it turns on the warning light. The freeze frame captured with P278B — engine load, rpm, temperature, speed — tells you exactly when the problem occurs, so reproduce those conditions when testing.

Common symptoms of P278B

the affected system operates intermittently or not at all
possible limp mode depending on the affected component
Check Engine Light on
increased fuel consumption in some cases

What causes P278B?

mechanical fault that the sensor correctly reports
degraded or drifting kick down switch
incorrect calibration after a module update or battery disconnect
faulty sensor or actuator of the affected circuit
blown fuse feeding the circuit
open or shorted wiring in the circuit
corroded, loose or damaged connector
poor ground connection
control module driver fault

How to diagnose P278B

Connect an OBD2 scanner, confirm P278B is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Visually inspect the wiring harness and connectors related to the kick down switch for damage, corrosion, chafing or poor contact.
Compare the kick down switch live reading against a known-good reference (specification or a correlated sensor) under the conditions from the freeze frame.
Measure reference voltage, ground and signal continuity at the component connector.
Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P278B does not return.

How to fix P278B

Start with the cheapest and most common causes before replacing expensive parts:

Replace the faulty sensor or actuator — $150–$500
Control module repair — $300–$1,000
Repair wiring or connectors — $80–$250

How much does it cost to fix P278B?

Repair cost depends on which component actually failed. Typical scenarios for P278B (parts and labor, USD, independent shop rates):

Replace the faulty sensor or actuator: $150–$500
Control module repair: $300–$1,000
Repair wiring or connectors: $80–$250

Overall, fixing P278B usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with P278B?