Poor or low voltage supply or ground to the engine control module (corroded or loose terminals, weak battery, charging fault); Damaged, corroded or loose connector or wiring at the engine control module; Internal fault in the engine control module's analogue-to-digital converter; Short or fault on a sensor reference voltage circuit pulling down the module's readings; Outdated or faulty module software where a manufacturer update is known for this code; Water ingress or heat damage to the module.

P1627

A/D Performance.

GMC
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
6: AreaComputer and output circuits
27: FaultThe specific fault in that area

What it means

On GMC vehicles P1627 means A/D Performance: the engine control module's internal analogue-to-digital converter failed a self-check. The module compares converted readings against expected values and saw a result outside the allowed range. This points to a fault inside the module or its power and ground supply rather than an ordinary sensor.

Symptoms

Malfunction indicator lamp on
Rough running or hesitation
Poor or erratic idle
Reduced power or limp-mode behaviour
Hard starting or intermittent no-start
Other sensor codes appearing at the same time

Possible causes

Poor or low voltage supply or ground to the engine control module (corroded or loose terminals, weak battery, charging fault)likely
Damaged, corroded or loose connector or wiring at the engine control modulepossible
Internal fault in the engine control module's analogue-to-digital converterpossible
Short or fault on a sensor reference voltage circuit pulling down the module's readingspossible
Outdated or faulty module software where a manufacturer update is known for this coderare
Water ingress or heat damage to the modulerare

How to diagnose

Read all stored codes and freeze frame data, noting whether other codes or voltage-related faults appear with P1627
Check battery condition and charging system voltage with the engine off and running
Inspect the engine control module connectors, fuses and relays for corrosion, moisture, bent pins or looseness
Check the module's power and ground circuits for voltage drop under load
Check sensor reference voltage circuits for shorts to ground or voltage, unplugging sensors one at a time if the reference voltage is pulled down
Clear the code and road test to see whether it returns, and whether it is intermittent or constant
Check for applicable service bulletins and whether a software update exists for your model and engine
If supply, grounds and wiring are all proven good and the code returns, test or replace the module and program it as the manufacturer specifies

How to fix

Repair or clean poor power and ground connections to the engine control module
Replace a weak battery or repair the charging fault
Repair damaged wiring or replace corroded connectors and terminals
Repair the circuit shorting a sensor reference voltage, or replace the faulty sensor
Update the module software if a manufacturer update addresses this code
Replace and program the engine control module if it is confirmed faulty

Can I keep driving?

Medium severity

The car may drive normally, but the module could behave unpredictably, so get it checked soon. Stop driving if it stalls, enters limp mode or runs very poorly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.