Open or high-resistance wiring in the TCS PWM signal circuit between the PCM and ABS module; Failed ABS control module, which is the most common source of a missing PWM output on GM vehicles; Corroded, backed-out, or damaged terminals at the PCM or ABS module connectors; Chafed or pinched harness in the engine bay or near the ABS pump assembly; Failed PCM driver for the PWM output, though this is less common than an ABS module fault; Poor ground connection at the ABS module or chassis ground point causing signal loss; Aftermarket electrical accessories or poor prior repairs splicing into the TCS circuit

DTC codes / GM codes / P1571

P1571 · GMTCS PWM Circuit No Frequency

Q: What does code P1571 mean?

TCS PWM Circuit No Frequency. P1571 on a GM vehicle means the powertrain control module (PCM) is monitoring the pulse-width-modulated (PWM) signal circuit for the traction control system (TCS) and has detected no frequency, meaning the expected digital signal is absent or not toggling. The PCM commands the antilock brake system (ABS) module to request torque reduction during traction control events, and this code sets when that PWM communication line stays flat instead of pulsing.

P1571 on a GM vehicle means the powertrain control module (PCM) is monitoring the pulse-width-modulated (PWM) signal circuit for the traction control system (TCS) and has detected no frequency, meaning the expected digital signal is absent or not toggling. The PCM commands the antilock brake system (ABS) module to request torque reduction during traction control events, and this code sets when that PWM communication line stays flat instead of pulsing.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyProfessional

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Traction control system (TCS) warning light illuminated steadily on the instrument cluster
ABS light may also be on because the ABS and TCS share the same module and wheel speed inputs
Traction control does not activate during wheel slip, allowing excessive spin on slippery surfaces
Cruise control may be disabled or drop out unexpectedly on some GM platforms
Often no symptoms besides the warning light, with normal braking and driveability otherwise
Reduced engine power message or limp-home behavior in rare cases where the PCM deems the fault severe

Common causes, most likely first

Open or high-resistance wiring in the TCS PWM signal circuit between the PCM and ABS module
Failed ABS control module, which is the most common source of a missing PWM output on GM vehicles
Corroded, backed-out, or damaged terminals at the PCM or ABS module connectors
Chafed or pinched harness in the engine bay or near the ABS pump assembly
Failed PCM driver for the PWM output, though this is less common than an ABS module fault
Poor ground connection at the ABS module or chassis ground point causing signal loss
Aftermarket electrical accessories or poor prior repairs splicing into the TCS circuit

How to diagnose and fix it

Connect a scan tool and read all ABS and PCM codes to confirm P1571 is current and check for related wheel speed sensor codes
Inspect the ABS module and PCM connectors for corrosion, backed-out pins, and tight terminal fit, then clean and reseat as needed
Use a digital multimeter or oscilloscope to check for a PWM signal on the TCS circuit at the ABS module and at the PCM while commanding a traction control event
Perform a wiggle test on the harness between the ABS module and PCM while watching live data or the scope to reveal intermittent opens
Check the ABS module ground circuit for excessive voltage drop under load and clean or repair the ground point
If the PWM signal is absent at the ABS module output but present at the PCM input, replace the ABS module and program it to the vehicle
Clear codes and verify the TCS lamp stays off through a full drive cycle including a traction control activation test

Why the ABS Module Is Usually the Culprit

Many technicians replace the PCM first because the code is stored there, but on GM vehicles the PWM signal originates at the ABS module, so the ABS module is the far more frequent failure point.
A missing frequency does not always mean a dead module; a single corroded terminal at the ABS connector can produce the exact same no-frequency condition and costs far less to fix.
Some GM platforms set P1571 as a secondary code when the ABS module loses power or ground intermittently, so always check for a companion ABS module communication code before condemning hardware.
Aftermarket stereos, alarm systems, or trailer wiring tapped into the wrong circuit can introduce noise or a short that kills the PWM signal, so inspect for non-factory wiring before replacing parts.
The TCS PWM circuit is separate from the wheel speed sensor circuits, so a car with P1571 can still have fully functional ABS while traction control is completely inoperative.

Can I keep driving with P1571?

The vehicle remains safe to drive in normal conditions because base braking and steering are unaffected, but traction control will not intervene on slippery surfaces. Avoid aggressive acceleration on wet, snowy, or loose surfaces and get the fault diagnosed promptly, especially before winter driving.

Tools that help

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