AutoCodes – Cadillac – P1635 Cadillac

P1635 Cadillac Code - 5-Volt Reference Circuit Low Conditions

Quick Answer

The Powertrain Control Module (PCM) uses a common 5.0 Volt Reference 1 circuit as a sensor feed. Common causes include A/C Pressure sensor harness is open or shorted, MAP sensor harness is open or shorted, EGR valve harness is open or shorted. 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: P1635 Cadillac indicates 5-Volt Reference Circuit Low Conditions.
Common causes: Common causes include A/C Pressure sensor harness is open or shorted, MAP sensor harness is open or shorted, EGR valve harness is open or shorted.
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 3,720

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 Sep 03, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P1635 Cadillac Description

The Powertrain Control Module (PCM) uses a common 5.0 Volt Reference 1 circuit as a sensor feed. This circuit supplies 5 Volts to the following sensors: The Air Condition (A/C) Pressure sensor, the Manifold Absolute Pressure (MAP) sensor, and the Engine Gas Recirculation (EGR) valve. The PCM monitors the voltage on the 5.0 Volt Reference 1 circuit.

OBDII Code P1635 Cadillac - 5-Volt Reference Circuit Low Conditions - AutoCodes.com — P1635 Cadillac Code - 5-Volt Reference Circuit Low Conditions

What does this mean?

What are the Possible Causes of the DTC P1635 Cadillac?

A/C Pressure sensor harness is open or shorted
MAP sensor harness is open or shorted
EGR valve harness is open or shorted

How to Fix the DTC P1635 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 P1635 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.