AutoCodes – GMC – P0842 2017 GMC Sierra

P0842 2017 GMC Sierra Code - Transmission Fluid Pressure Switch 1 Circuit Low Voltage

Quick Answer

The Transmission Fluid Pressure (TFP) switch 1 is part of the control solenoid valve assembly, which has no serviceable parts. Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty Transmission Control Solenoid Valve Assembly. 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: P0842 2017 GMC Sierra indicates Transmission Fluid Pressure Switch 1 Circuit Low Voltage.
Common causes: Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty Transmission Control Solenoid Valve Assembly.
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 210

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 Aug 02, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0842 2017 GMC Sierra Description

The Transmission Fluid Pressure (TFP) switch 1 is part of the control solenoid valve assembly, which has no serviceable parts. The Transmission Control Module (TCM) supplies a signal circuit to the TFP Switch 1. The TFP Switch 1 has an internal case ground. TFP Switch 1 is normally closed or LOW. When oil pressure is present at the TFP Switch 1, the switch is open or HIGH. The normally high clutch pressure control (PC) solenoid 2 controls pressure to the 3-5 reverse clutch regulator valve. The TCM monitors the TFP switch 1 to determine the position of the 3-5 reverse clutch regulator valve. When the 3-5 reverse clutch is commanded OFF, pressure is present on the TFP switch 1. When the 3-5 reverse clutch is commanded ON, the 3-5 reverse clutch regulator valve moves and pressure to the TFP switch 1 is exhausted through the 3-5 reverse clutch regulator valve. The Diagnostic Trouble Code (DTC) will be set when the TCM detects that the TFP switch 1 signal voltage remains LOW after the 3-5-R clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 25 counts are accumulated.

OBDII Code P0842 2017 GMC Sierra - Transmission Fluid Pressure Switch 1 Circuit Low Voltage - AutoCodes.com — P0842 2017 GMC Sierra Code - Transmission Fluid Pressure Switch 1 Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P0842 2017 GMC Sierra?

Low transmission fluid level
Dirty transmission fluid
Faulty Transmission Control Solenoid Valve Assembly
Transmission Control Solenoid Valve Assembly harness is open or shorted
Transmission Control Solenoid Valve Assembly circuit poor electrical connection

How to Fix the DTC P0842 2017 GMC Sierra?

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 P0842 2017 GMC Sierra 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.

Need more information about the P0842 2017 GMC Sierra code?

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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 P0842 2017 GMC Sierra Code

1. What does the OBDII code P0842 mean on a 2017 GMC Sierra?

Code P0842 indicates a "Transmission Fluid Pressure Switch 1 Circuit Low Voltage," meaning the transmission control module (TCM) has detected an issue with the voltage signal from the transmission fluid pressure sensor.

2. What are the common symptoms of P0842 in a 2017 GMC Sierra?

Symptoms may include erratic or delayed shifting, transmission stuck in one gear, harsh gear engagement, the check engine light illuminated, and reduced fuel efficiency.

3. What causes the P0842 code to appear on a 2017 GMC Sierra?

Possible causes include a faulty transmission fluid pressure sensor, damaged or corroded wiring or connectors, low transmission fluid levels, or a malfunction in the transmission control module (TCM).

4. Can driving with a P0842 code damage my 2017 GMC Sierra?

Driving with this code can cause further damage to the transmission if the issue is related to low fluid pressure or a critical sensor failure. Itâ€™s best to address the problem promptly.

5. How do I diagnose the P0842 code on my 2017 GMC Sierra?

Diagnosis involves using an OBDII scanner to confirm the code, inspecting the transmission fluid pressure sensor and wiring for damage, checking fluid levels and condition, and testing the sensorâ€™s voltage output with a multimeter.

6. Can low transmission fluid cause the P0842 code on a 2017 GMC Sierra?

Yes, low or dirty transmission fluid can affect fluid pressure readings and trigger the P0842 code. Always check and refill the fluid to the proper level if needed.

7. How do you fix the P0842 code on a 2017 GMC Sierra?

Repairs may include replacing the transmission fluid pressure sensor, repairing damaged wiring or connectors, topping off or replacing the transmission fluid, or, in rare cases, replacing the TCM.

8. How much does it cost to fix the P0842 code on a 2017 GMC Sierra?

The cost can range from $100 to $400 or more, depending on whether it involves sensor replacement, wiring repairs, or more extensive transmission work.

9. Does the P0842 code require resetting after repairs on a 2017 GMC Sierra?

Yes, after completing repairs, the code should be cleared using an OBDII scanner. If the issue is resolved, the code should not return.

10. Can a faulty TCM cause the P0842 code on a 2017 GMC Sierra?

While rare, a malfunctioning TCM can potentially cause the P0842 code by failing to interpret or transmit correct signals from the pressure sensor. This should be the last item to check after ruling out other causes.