OBD Guide

P1A78

Starter/Generator Control Module Coolant Temperature Sensor 3 Performance

P1A78 is an OBD-II diagnostic trouble code meaning: Starter/Generator Control Module Coolant Temperature Sensor 3 Performance. Common causes: coolant temperature sensor malfunction, open or short circuit in the sensor circuit. Estimated repair cost: $17–56.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$17–56 (est.)

Symptoms

  • Check Engine light comes on
  • Problems starting the engine
  • Reduced hybrid system efficiency (if applicable)
  • Unstable engine operation
  • Increased fuel consumption

Causes

  • Coolant temperature sensor malfunction
  • Open or short circuit in the sensor circuit
  • Poor contact in the sensor connector
  • Starter/Generator Control Module Malfunction
  • Wiring Harness Problems

How to Fix

  1. Check the condition of the coolant temperature sensor
  2. Check the integrity of the sensor circuit and connection
  3. Check connectors and contacts for corrosion or damage
  4. Replace the faulty coolant temperature sensor
  5. If necessary, replace the starter/generator control module

Related codes

FAQ

What does the P1A78 code mean?

P1A78 is an OBD-II diagnostic trouble code that indicates: Starter/Generator Control Module Coolant Temperature Sensor 3 Performance

What causes a P1A78 error code?

The most common causes of P1A78 include: Coolant temperature sensor malfunction; Open or short circuit in the sensor circuit; Poor contact in the sensor connector; Starter/Generator Control Module Malfunction.

How do I fix a P1A78 diagnostic trouble code?

To fix P1A78: Check the condition of the coolant temperature sensor. Check the integrity of the sensor circuit and connection. Check connectors and contacts for corrosion or damage. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1A78?

Yes, but get it checked soon

How much does it cost to fix P1A78?

The estimated repair cost for P1A78 is $17–56. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat