AutoCodes – Cadillac – P1838 Cadillac

P1838 Cadillac Code - Internal Mode Switch 'A' Circuit High Voltage

Quick Answer

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode 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: P1838 Cadillac indicates Internal Mode Switch 'A' Circuit High Voltage.
Common causes: Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode 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 1,197

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 Mar 23, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1838 Cadillac Description

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate hall effect switches. Each hall effect switch is supplied with a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70–0.96 V indicating On or 1.68–2.38 V indicating Off. The voltage values on each internal mode switch circuit will change and are dependent on the position of the gear selector. The state of each internal mode switch A/B/C/P/S signal circuit is displayed on the scan tool. The Diagnostic Trouble Code (DTC) will be set when the TCM has detected the internal mode switch A signal circuit voltage is greater than 2.38 V, for 1.75 s.

OBDII Code P1838 Cadillac - Internal Mode Switch 'A' Circuit High Voltage - AutoCodes.com — P1838 Cadillac Code - Internal Mode Switch 'A' Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P1838 Cadillac?

Faulty Transmission Internal Mode Switch
Transmission Internal Mode Switch harness is open or shorted
Transmission Internal Mode Switch circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P1838 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 P1838 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 P1838 Cadillac Code

1. What are the common symptoms of OBDII code P1838 in a Cadillac related to the Internal Mode Switch 'A' Circuit High Voltage?

The common symptoms include issues with shifting gears, erratic shifting behavior, transmission slipping, and potentially triggering the vehicle into "limp mode."

2. What are the possible causes of the Internal Mode Switch 'A' Circuit High Voltage code P1838 in a Cadillac?

Possible causes include a faulty internal mode switch, damaged wiring or connectors in the circuit, a malfunctioning PCM (powertrain control module), or a short circuit in the system.

3. How can I diagnose the Internal Mode Switch 'A' Circuit High Voltage code P1838 in my Cadillac?

Diagnosis typically involves using a scan tool to retrieve the code, inspecting the internal mode switch and its connections, checking the wiring for any damage or shorts, and testing the PCM for proper function.

4. Can I continue driving my Cadillac with OBDII code P1838 present?

It is not recommended to continue driving with this code present, as it can lead to further transmission issues and potential safety hazards. It's best to address the problem promptly.

5. How can I repair the Internal Mode Switch 'A' Circuit High Voltage code P1838 in my Cadillac?

Repair may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, resetting the PCM, or seeking assistance from a professional mechanic for a thorough diagnosis and repair.

6. Will resetting the OBDII code P1838 in my Cadillac make the problem go away?

Resetting the code may temporarily clear the warning light, but it will not fix the underlying issue causing the code. It is important to diagnose and address the root cause of the problem.

7. How much does it typically cost to repair OBDII code P1838 in a Cadillac?

The cost of repairs can vary depending on the exact cause of the code and the labor rates in your area. It's advisable to get a diagnosis from a mechanic to determine the cost accurately.

8. Can a DIY enthusiast fix the Internal Mode Switch 'A' Circuit High Voltage code P1838 issue in a Cadillac?

While some DIY enthusiasts may have the skills to diagnose and repair this issue, it is a complex problem related to the transmission system. It is recommended to seek professional help for an accurate and safe repair.

9. Is OBDII code P1838 in a Cadillac a common problem?

While it may not be as common as some other OBDII codes, issues related to the internal mode switch and transmission circuits can occur in Cadillacs and other vehicles. Prompt attention is key to preventing further damage.

10. How can I prevent OBDII code P1838 from occurring in my Cadillac in the future?

Regular maintenance, including checking and servicing the transmission system, inspecting wiring and connectors for damage, and addressing any issues promptly, can help prevent the recurrence of this code.