B138A - Control Module Voltage Reference Output Circuit

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3    What is this?
Table of contents

B138A Possible Causes

  • Faulty Rear Parking Assist Alarm Sensor
  • Rear Parking Assist Alarm Sensor harness is open or shorted
  • Rear Parking Assist Alarm Sensor circuit poor electrical connection
  • Faulty Parking Assist Control Module

How do I fix code B138A?

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
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Tech Notes

DTC B138A 03: Control Module Voltage Reference Output Circuit Low Voltage
DTC B138A 07: Control Module Voltage Reference Output Circuit High Voltage

Cost of diagnosing the B138A code

Labor: 1.0

The cost of diagnosing the B138A code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

B138A Description

The object sensors are 3-wire sensors that are used to determine the distance between the vehicle and an object of interest. The Parking Assist Control Module supplies 8 V to the object sensors via the 8 V reference circuit and provides ground via the low reference circuit. The Parking Assist Control Module triggers the sensors in a sequential loop. After each sensor transmits, the Parking Assist Control Module uses the sensor echo received through the signal circuit to calculate the distance and position of an object.
OBDII Code B138a - Control Module Voltage Reference Output Circuit - AutoCodes.com

More Information

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Information for specific makes

  • B138A BUICK Control Module Voltage Reference Output Circuit
  • B138A CADILLAC Control Module Voltage Reference Output Circuit
  • B138A CHEVROLET Control Module Voltage Reference Output Circuit
  • B138A GMC Control Module Voltage Reference Output Circuit

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