AutoCodes – GMC – P1758 GMC

P1758 GMC Code - Transmission Range Switch Indicates Drive Without Drive Ratio

Quick Answer

The Transmission Range (TR) switch is part of the park/neutral position and back-up lamp switch assembly and is mounted on the transmission manual shaft. Common causes include Faulty Transmission Range (TR) Switch, Transmission Range Switch harness is open or shorted, Transmission Range Switch 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: P1758 GMC indicates Transmission Range Switch Indicates Drive Without Drive Ratio.
Common causes: Common causes include Faulty Transmission Range (TR) Switch, Transmission Range Switch harness is open or shorted, Transmission Range Switch 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 381

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 Feb 03, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1758 GMC Description

The Transmission Range (TR) switch is part of the park/neutral position and back-up lamp switch assembly and is mounted on the transmission manual shaft. The TR switch is a multi-signal switch. The fuse block supplies ignition voltage to the TR switch on four signal circuits, A, B, C, and P. Each gear selector lever position powers two or more of the signal circuits in a unique pattern. In order to determine the gear range selected by the driver, the TCM compares the voltage combination on the signal circuits to a TR switch combination table stored in memory. Refer to Transmission Range Switch Logic. When the TCM detects the combination of TR switch signals for a forward range and the vehicle is not moving, Diagnostic Trouble Code (DTC) P1758 sets. DTC P1758 is a type B DTC.

OBDII Code P1758 GMC - Transmission Range Switch Indicates Drive Without Drive Ratio - AutoCodes.com — P1758 GMC Code - Transmission Range Switch Indicates Drive Without Drive Ratio

What does this mean?

What are the Possible Causes of the DTC P1758 GMC?

Faulty Transmission Range (TR) Switch
Transmission Range Switch harness is open or shorted
Transmission Range Switch circuit poor electrical connection

How to Fix the DTC P1758 GMC?

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 P1758 GMC 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 P1758 GMC Code

1. What does the OBDII code P1758 mean on a GMC vehicle?

P1758 indicates that the transmission range switch has detected the vehicle is in Drive, but the transmission is not achieving the correct gear ratio for Drive.

2. What are the common symptoms of the P1758 code in a GMC?

Symptoms may include the Check Engine Light turning on, poor acceleration, transmission slipping, difficulty shifting gears, or reduced fuel efficiency.

3. What causes the P1758 code to appear on a GMC vehicle?

Common causes include a faulty transmission range switch, damaged wiring or connectors in the transmission system, a malfunctioning transmission control module (TCM), or internal transmission issues.

4. Can I continue driving my GMC with a P1758 code?

It is not recommended, as driving with this issue can lead to further damage to your transmission and potentially leave you stranded.

5. How is the P1758 code diagnosed in a GMC?

A mechanic will use a scan tool to retrieve the code, inspect the transmission range switch, check the wiring and connectors, and monitor live data to confirm the fault.

6. What repairs are typically required to fix a P1758 code on a GMC?

Repairs may include replacing the transmission range switch, repairing or replacing damaged wiring, reprogramming or replacing the TCM, or addressing internal transmission issues.

7. How much does it cost to fix a P1758 code on a GMC vehicle?

The cost can vary depending on the root cause but typically ranges from $150 to $500 for parts and labor, with more extensive transmission repairs costing significantly more.

8. Can a faulty transmission control module cause the P1758 code?

Yes, a malfunctioning TCM can cause improper communication with the transmission, leading to this code.

9. Is the P1758 code specific to GMC vehicles?

No, while it is commonly associated with GMC vehicles, the code can also appear on other makes and models with similar transmission setups.

10. How can I prevent the P1758 code from appearing in the future?

Regular maintenance, including transmission fluid changes, inspecting wiring and connectors, and addressing minor transmission issues promptly, can help prevent this code.