P2743 — Transmission Fluid Temperature Sensor "B" Circuit High

P2743 — Transmission Fluid Temperature Sensor "B" Circuit High. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: valve body wear, faulty transmission speed sensor, failed shift or pressure control solenoid.

powertrain (engine/transmission)

Is it safe to drive?

Drive with caution Drive only if the transmission still shifts predictably, and avoid highway speeds. Driving with slipping or limp mode accelerates internal wear — every kilometre can add to the final repair bill.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P2743 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. 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.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the automatic transmission control for damage, corrosion, chafing or poor contact.
  4. Subsystem check With the transmission fluid temperature sensor "B" disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
  5. Subsystem check Check transmission fluid level and condition — dark, burnt fluid points to internal wear.
  6. Subsystem check Read transmission-specific codes and live data (solenoid states, input/output speed) with a capable scanner.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2743 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P2743 (parts and labor, USD, independent shop rates): Transmission fluid service: $150–$350; Transmission rebuild or replacement: $2,500–$5,500; Replace a shift solenoid: $300–$800; Valve body repair or replacement: $700–$1,500. Overall, fixing P2743 usually costs between $150 and $5,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How do I diagnose P2743 myself?

Start with a scan: confirm P2743, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the transmission fluid temperature sensor "B", and verify the suspect component against live data before buying parts.

Will P2743 clear itself?

Sometimes P2743 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of P2743?

Drivers most often notice: Check Engine or transmission warning light on, transmission stuck in one gear (limp mode), harsh or delayed shifting, no movement in severe cases.

How much does it cost to fix P2743?

Transmission fluid service — $150–$350; Transmission rebuild or replacement — $2,500–$5,500; Replace a shift solenoid — $300–$800; Valve body repair or replacement — $700–$1,500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does OBD2 code P2743 mean?

P2743 — Transmission Fluid Temperature Sensor "B" Circuit High. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: valve body wear, faulty transmission speed sensor, failed shift or pressure control solenoid.

What does P2743 mean?

P2743 is logged by the onboard diagnostics when the automatic transmission control does not behave as expected. The official definition is “Transmission Fluid Temperature Sensor "B" Circuit High”. This is a powertrain (engine/transmission) category code.

“Circuit high” means the control module sees a voltage on the transmission fluid temperature sensor "B" circuit that is above the expected range — typically close to battery voltage. Physically this points to a short to a power feed, a broken ground return, or a failed component pulling the signal line high.

To set P2743, the control module compares live readings of the automatic transmission control against calibrated limits, usually over several drive cycles. Alongside the code it stores a freeze frame — a snapshot of rpm, load, coolant temperature and vehicle speed at the moment of failure. Reading that snapshot first saves diagnostic time.

What causes P2743?

  • signal wire shorted to battery positive
  • failed transmission fluid temperature sensor "B" pulling the signal high
  • open ground return of the transmission fluid temperature sensor "B"
  • low or degraded transmission fluid
  • failed shift or pressure control solenoid
  • faulty transmission speed sensor
  • internal mechanical wear (clutches, torque converter)
  • wiring or connector faults in the valve body harness

Common symptoms of P2743

  • Check Engine or transmission warning light on
  • transmission stuck in one gear (limp mode)
  • harsh or delayed shifting
  • no movement in severe cases
  • shuddering at highway speed

How to diagnose P2743

  1. Connect an OBD2 scanner, confirm P2743 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. 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.
  3. Visually inspect the wiring harness and connectors related to the automatic transmission control for damage, corrosion, chafing or poor contact.
  4. With the transmission fluid temperature sensor "B" disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
  5. Check transmission fluid level and condition — dark, burnt fluid points to internal wear.
  6. Read transmission-specific codes and live data (solenoid states, input/output speed) with a capable scanner.
  7. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2743 does not return.

How to fix P2743

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

  • Transmission fluid service — $150–$350
  • Transmission rebuild or replacement — $2,500–$5,500
  • Replace a shift solenoid — $300–$800
  • Valve body repair or replacement — $700–$1,500

How much does it cost to fix P2743?

Repair cost depends on which component actually failed. Typical scenarios for P2743 (parts and labor, USD, independent shop rates):

  • Transmission fluid service: $150–$350
  • Transmission rebuild or replacement: $2,500–$5,500
  • Replace a shift solenoid: $300–$800
  • Valve body repair or replacement: $700–$1,500

Overall, fixing P2743 usually costs between $150 and $5,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with P2743?

Drive only if the transmission still shifts predictably, and avoid highway speeds. Driving with slipping or limp mode accelerates internal wear — every kilometre can add to the final repair bill.

Related OBD2 codes