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P1891 Cadillac Code - Throttle Position Sensor PWM Signal Low

Quick Answer

When a Cadillac vehicle triggers the P1891 diagnostic trouble code (DTC), it indicates a problem with the Throttle Position Sensor (TPS) PWM (Pulse Width Modulation) signal being too low. Common causes include Faulty Throttle Position Sensor (TPS), Wiring or connector issues, Vacuum leaks. 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
P1891 Cadillac indicates Throttle Position Sensor PWM Signal Low.
Common causes
Common causes include Faulty Throttle Position Sensor (TPS), Wiring or connector issues, Vacuum leaks.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 09, 2024
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Code P1891 Cadillac Description

When a Cadillac vehicle triggers the P1891 diagnostic trouble code (DTC), it indicates a problem with the Throttle Position Sensor (TPS) PWM (Pulse Width Modulation) signal being too low. The TPS is a crucial component that monitors the position of the throttle valve and sends this information to the Engine Control Module (ECM). The PWM signal refers to the way in which the TPS communicates with the ECM, using varying pulse widths to convey throttle position data.

OBDII Code P1891 Cadillac - Throttle Position Sensor PWM Signal Low
P1891 Cadillac Code - Throttle Position Sensor PWM Signal Low

Common Causes of P1891 Cadillac

  1. Faulty Throttle Position Sensor (TPS)
  2. Wiring or connector issues
  3. Vacuum leaks
  4. ECM malfunction
  5. Poor electrical connections

Symptoms of P1891 Cadillac

  1. Erratic throttle response
  2. Poor acceleration
  3. Stalling or rough idling
  4. Transmission shifting problems
  5. Check Engine Light illuminated

How to Fix P1891 Cadillac

  1. Diagnose the issue by using a scan tool to confirm the P1891 code and testing the TPS sensor for proper operation.
  2. Inspect the wiring harness and connectors for any signs of damage or corrosion, repairing or replacing as needed.
  3. Check for vacuum leaks in the intake system and address any leaks found.
  4. Replace the Throttle Position Sensor if it is determined to be faulty, ensuring proper installation and calibration.
  5. Clear the DTC and perform a test drive to verify that the issue has been resolved.

Cost to Fix P1891 Cadillac

The cost of repairing a Throttle Position Sensor PWM Signal Low issue can vary depending on the specific cause of the problem and the labor rates in your area. Typically, replacing a TPS sensor can range from $100 to $300, with additional costs for diagnostic time and labor. Overall, you can expect a total repair cost of approximately $200 to $500, including parts and labor. Keep in mind that rates can fluctuate based on location, vehicle make and model, and shop rates, so it's advisable to consult with a qualified mechanic for a more accurate estimate.

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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 P1891 Cadillac Code

1. What does the OBDII code P1891 mean for a Cadillac?

P1891 indicates that the Throttle Position Sensor (TPS) PWM signal is low, which suggests an issue with the sensor or its circuit.

2. What are the common symptoms of code P1891 in a Cadillac?

Symptoms may include poor acceleration, reduced fuel efficiency, engine hesitation, or irregular idle.

3. What causes the P1891 code to appear?

Common causes include a faulty Throttle Position Sensor, wiring issues, connector problems, or a malfunctioning PCM.

4. Can I drive my Cadillac with the P1891 code?

While the vehicle may still be drivable, prolonged operation with this code can lead to performance issues and potential damage to other components.

5. How do I diagnose the P1891 code?

Use a scan tool to confirm the code, visually inspect the TPS and its wiring, and test the sensor’s voltage and signal output.

6. How do I fix the P1891 code on a Cadillac?

Repairs may include replacing the TPS, repairing or replacing damaged wiring, cleaning the connectors, or updating the PCM software.

7. How much does it cost to repair the P1891 code?

The cost can vary but typically ranges from $100 to $300 for parts and labor, depending on the extent of the issue.

8. Can a dirty throttle body cause the P1891 code?

Yes, a dirty throttle body can affect TPS operation and potentially trigger this code.

9. Will resetting the code fix the issue permanently?

Resetting the code may clear it temporarily, but the underlying issue must be resolved to prevent it from returning.

10. What happens if I ignore the P1891 code?

Ignoring the code can lead to worsening engine performance, reduced fuel efficiency, and potential damage to the throttle system.

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