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P077D Cadillac Code - Transmission Output Speed Sensor Circuit High Voltage

Quick Answer

The Output Speed Sensor (OSS) is a hall-effect type sensor. Common causes include Faulty Transmission Output Speed Sensor (OSS), Transmission Output Speed Sensor harness is open or shorted, Transmission Output Speed Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P077D Cadillac indicates Transmission Output Speed Sensor Circuit High Voltage.
Common causes: Common causes include Faulty Transmission Output Speed Sensor (OSS), Transmission Output Speed Sensor harness is open or shorted, Transmission Output Speed Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 339

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 29, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P077D Cadillac Description

The Output Speed Sensor (OSS) is a hall-effect type sensor. The OSS mounts to the automatic transmission case assembly and connects to the control solenoid valve assembly through a 2-wire harness and connector. The sensor faces the park gear teeth. The sensor receives battery voltage on the OSS supply voltage circuit from the Transmission Control Module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the park gear teeth. This signal is transmitted through the OSS signal circuit to the TCM. The TCM uses the OSS signal to determine line pressure, transmission shift patterns, vehicle speed, and gear ratio.
The Diagnostic Trouble Code (DTC) will be set when the TCM detects the vehicle speed sensor signal circuit voltage is 4.75 V or greater for 0.8 s.

OBDII Code P077D Cadillac - Transmission Output Speed Sensor Circuit High Voltage - AutoCodes.com — P077D Cadillac Code - Transmission Output Speed Sensor Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P077D Cadillac?

Faulty Transmission Output Speed Sensor (OSS)
Transmission Output Speed Sensor harness is open or shorted
Transmission Output Speed Sensor circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P077D Cadillac?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P077D Cadillac code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P077D Cadillac Code

1. What does the OBDII code P077D mean on a Cadillac?

P077D indicates a high voltage issue in the transmission output speed sensor circuit, which monitors the rotational speed of the transmission output shaft.

2. What are the common symptoms of the P077D code on a Cadillac?

Symptoms may include erratic shifting, transmission slipping, poor acceleration, or the vehicle going into limp mode. The check engine light may also be illuminated.

3. What causes the P077D code on a Cadillac?

Common causes include a faulty output speed sensor, damaged wiring or connectors in the sensor circuit, or issues with the transmission control module (TCM).

4. Can I drive my Cadillac with the P077D code active?

It is not recommended to drive with the P077D code active, as it may lead to further transmission damage or unsafe driving conditions due to erratic shifting.

5. How do I diagnose the P077D code on my Cadillac?

Diagnosis involves using an OBDII scanner to confirm the code, inspecting the output speed sensor and its wiring for damage, and testing the sensor's electrical resistance and voltage levels.

6. How do I fix the P077D code on my Cadillac?

Repairs may include replacing a faulty output speed sensor, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the transmission control module if needed.

7. How much does it cost to fix the P077D code on a Cadillac?

Repair costs can vary, but replacing the output speed sensor typically costs $100â€“$300, including parts and labor. Wiring repairs or TCM replacement may cost more.

8. Can a faulty speed sensor cause other issues besides the P077D code?

Yes, a faulty output speed sensor can cause other transmission-related codes, reduced fuel efficiency, and issues with cruise control or speedometer functionality.

9. Can I reset the P077D code without fixing the issue?

While clearing the code with an OBDII scanner may temporarily turn off the check engine light, the problem will likely return if the underlying issue is not resolved.

10. Is the P077D code related to the transmission output speed sensor only?

Primarily, yes, but the issue could also stem from related components such as the wiring, connectors, or the TCM that interacts with the speed sensor.