Damaged, chafed, or corroded wiring on the driver 5 line 1 circuit between the PCM and the ETC module; Poor connection or loose pins at the PCM or ETC module connectors; Failed electronic throttle control (ETC) module or throttle body assembly; Internal fault in the powertrain control module (PCM) affecting the communication line; Electrical interference or a short to voltage or ground on the data line; Low battery voltage or poor grounds causing communication errors

DTC codes / GM codes / P1681

P1681 · GMDriver 5 Line 1

Q: What does code P1681 mean?

Driver 5 Line 1. P1681 on GM vehicles indicates that the powertrain control module (PCM) has detected a fault on the serial data communication line it uses to talk to the electronic throttle control (ETC) module, often called driver 5 line 1. The PCM monitors this dedicated data circuit for expected messages and voltage levels, and it sets the code when the signal is missing, corrupted, or out of range, which can affect throttle response and other functions.

P1681 on GM vehicles indicates that the powertrain control module (PCM) has detected a fault on the serial data communication line it uses to talk to the electronic throttle control (ETC) module, often called driver 5 line 1. The PCM monitors this dedicated data circuit for expected messages and voltage levels, and it sets the code when the signal is missing, corrupted, or out of range, which can affect throttle response and other functions.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyProfessional

AreaComputer and output circuits

Symptoms you may notice

Illuminated check engine light or reduced power message on the dashboard
Often no symptoms besides the warning light, especially if the fault is intermittent
Reduced engine power or limp mode with limited throttle response
Rough idle or stalling when the communication loss affects idle control
Inconsistent or delayed acceleration when pressing the accelerator pedal
Other warning lights such as stability control or traction control may illuminate

Common causes, most likely first

Damaged, chafed, or corroded wiring on the driver 5 line 1 circuit between the PCM and the ETC module
Poor connection or loose pins at the PCM or ETC module connectors
Failed electronic throttle control (ETC) module or throttle body assembly
Internal fault in the powertrain control module (PCM) affecting the communication line
Electrical interference or a short to voltage or ground on the data line
Low battery voltage or poor grounds causing communication errors

How to diagnose and fix it

Inspect the battery state of charge and clean all engine and chassis grounds to rule out low-voltage communication faults
Visually inspect the driver 5 line 1 wiring harness between the PCM and ETC module for chafing, corrosion, or loose connectors
Disconnect the PCM and ETC module connectors and check for bent pins, pushed-out terminals, or water intrusion
Use a digital multimeter to check continuity and resistance on the driver 5 line 1 circuit, looking for opens or excessive resistance
Check for shorts to voltage or ground on the data line with the key on and modules disconnected
If wiring and connections are good, swap in a known-good ETC module or throttle body to test for a faulty module
If the fault persists after all other checks, diagnose or replace the PCM, followed by relearn and verification procedures

What most technicians miss on P1681

A loose or corroded ground connection at the ETC module or PCM can mimic a failed module and set P1681 without any wiring damage on the data line itself.
Intermittent P1681 codes often appear after battery replacement or jump-starting because voltage spikes disturb the communication line, so clear the code and test-drive before condemning parts.
The driver 5 line 1 circuit is a dedicated serial data link, not the generic CAN bus, so a scan tool that only checks CAN communication may not reveal the fault.
After replacing the ETC module or PCM, a throttle relearn or idle relearn procedure is required, and skipping it can cause the code to return immediately.
A failing throttle body motor or position sensor can disrupt the data line and set P1681 even when the wiring tests perfectly, so always check for related throttle body codes.

Can I keep driving with P1681?

If the vehicle is in reduced power mode or the throttle response is unpredictable, avoid driving and have it towed to a repair shop. If the only symptom is a warning light and the car drives normally, you can drive cautiously to a service location, but avoid heavy acceleration or towing until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.