AutoCodes – Pontiac – P1820 Pontiac

P1820 Pontiac Code - Internal Mode Switch Circuit 'A' Low

Quick Answer

With the engine runtime over 5 seconds, system voltage from 8-18v, Fuel Cutoff inactive, engine torque from 30-148 ft-lb (40-200 Nm), the Powertrain Control Module (PCM) detects that the Internal Mode Switch (IMS) signal indicated PARK for 2 seconds and then the IMS indicated a transitional state between D4 and D3, conditions met for 5 seconds. Common causes include Faulty Internal Mode Switch, Internal Mode Switch harness is open or shorted, 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: P1820 Pontiac indicates Internal Mode Switch Circuit 'A' Low.
Common causes: Common causes include Faulty Internal Mode Switch, Internal Mode Switch harness is open or shorted, 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 1,488

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Sep 21, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1820 Pontiac Description

OBDII Code P1820 Pontiac - Internal Mode Switch Circuit 'A' Low - AutoCodes.com — P1820 Pontiac Code - Internal Mode Switch Circuit 'A' Low

What does this mean?

What are the Possible Causes of the DTC P1820 Pontiac?

Faulty Internal Mode Switch
Internal Mode Switch harness is open or shorted
Internal Mode Switch circuit poor electrical connection

How to Fix the DTC P1820 Pontiac?

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 P1820 Pontiac 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 P1820 Pontiac Code

1. What does the OBDII code P1820 mean for a Pontiac?

Code P1820 indicates an issue with the Internal Mode Switch (IMS) Circuit 'A', which is responsible for detecting the gear position in the transmission. A low voltage condition has been detected in the circuit.

2. What are common symptoms of the P1820 code in a Pontiac?

Symptoms may include harsh or erratic shifting, the vehicle stuck in one gear, the transmission not engaging properly, or the illumination of the Check Engine Light.

3. What causes the P1820 code to appear on a Pontiac?

Common causes include a faulty Internal Mode Switch (IMS), damaged wiring or connectors in the transmission circuit, a malfunctioning transmission control module (TCM), or low transmission fluid levels.

4. Can I drive my Pontiac with the P1820 code?

Driving with this code is not recommended, as it can cause further damage to the transmission and lead to unsafe driving conditions due to shifting issues.

5. How do you diagnose a P1820 code on a Pontiac?

Diagnosis typically involves using a scan tool to confirm the code, inspecting the IMS and its wiring for damage, checking for proper voltage and continuity in the circuit, and ensuring the transmission fluid level is correct.

6. Is the Internal Mode Switch the same as the transmission range sensor?

Yes, in many vehicles, including Pontiacs, the Internal Mode Switch is often integrated with the transmission range sensor and performs gear position detection.

7. What repairs can fix the P1820 code?

Repairs may include replacing the Internal Mode Switch, repairing or replacing damaged wiring or connectors, updating or reprogramming the TCM, or replacing it if necessary.

8. How much does it cost to fix a P1820 code on a Pontiac?

Repair costs vary but typically range from $200 to $500, depending on whether the IMS needs replacement or if additional wiring or module repairs are required.

9. Can low transmission fluid cause the P1820 code?

Yes, low or contaminated transmission fluid can potentially cause issues with the Internal Mode Switch, leading to the P1820 code.

10. How can I prevent the P1820 code from recurring on my Pontiac?

Regular maintenance, including checking and replacing transmission fluid as needed, inspecting electrical connections, and addressing transmission issues promptly, can help prevent this code from recurring.