01 Inside the Day of an Automotive Engineer: Roles, Responsibi… • 02 You Could Be Slowly Killing Your Engine Without Realizing Y… • 03 Does Auto Start - Stop Wear Out a Starter? • 04 Common Causes of Turbocharger Damage and How to Avoid Them • 05 Can a Hybrid Car Be Turbo Charged or Super Charged? • 06 LED vs Halogen Headlights: Which One is Better for Your Car? • 07 P0071 Code: Ambient Air Temperature Sensor Range or Perform… • 08 General Motors: A History of Innovation and Leadership • 09 B0017 and B0018: Right Front or Passenger Frontal Deploymen… • 10 The Challenges of CVT Gearboxes: Troubleshooting and Repair •

DTC codes / GM codes / P1529

P1529 · GMHeated Windshield Request Problem

P1529 on a GM vehicle means the body control module (BCM) has detected a problem with the heated windshield request circuit, typically when the windshield wiper or defrost request signal does not match the expected voltage or state. The computer is not reporting a failed wiper motor or a bad switch directly; it is flagging that the request line from the wiper switch or HVAC control head is out of range or inconsistent with other inputs.

SystemPowertrain
Code typeGM specific
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The heated windshield function does not activate when the defrost or heated glass button is pressed.
  • The windshield wipers may park incorrectly, run only at one speed, or fail to return to the rest position.
  • The heated windshield indicator light may flash or stay off entirely despite a button press.
  • Often no symptoms besides the warning light, especially if the fault is intermittent or only affects the request signal.
  • The rear defroster or heated mirrors may also be inoperative if they share the same request circuit or ground.
  • In cold weather, the windshield may not clear ice or fog as quickly as expected because the heating grid never energizes.

Common causes, most likely first

  1. A faulty windshield wiper switch or multifunction stalk that sends an incorrect heated windshield request signal.
  2. Corroded, loose, or damaged wiring and connectors in the heated windshield request circuit, often at the wiper motor or BCM harness.
  3. A failed body control module (BCM) that misreads the request input or has an internal driver fault.
  4. A bad ground connection shared by the wiper motor, HVAC control head, and heated windshield relay, causing voltage drops that confuse the BCM.
  5. A shorted or open heated windshield relay coil or control circuit that prevents the BCM from seeing the expected feedback.
  6. Water intrusion into the wiper motor connector or BCM kick panel area, common on older GM trucks and SUVs with clogged cowl drains.
  7. An aftermarket remote start or alarm installation that tapped into the wiper or defrost request wire and disturbed the signal.

How to diagnose and fix it

  1. Connect a scan tool and read all BCM and HVAC codes to confirm P1529 is current and not a history code from a previous low-voltage event.
  2. Inspect the wiper switch and HVAC control head connectors for corrosion, pushed pins, or loose terminals, then clean and reseat them.
  3. Check the heated windshield relay and its socket for burn marks or a missing relay, and swap it with a known-good relay of the same part number.
  4. Measure voltage and resistance on the request signal wire from the wiper switch to the BCM while pressing the heated windshield button, looking for a clean transition between rest and request voltages.
  5. Perform a voltage drop test on the ground circuit at the wiper motor and BCM to rule out a bad ground that is skewing the request signal.
  6. If the signal wire and grounds are good, substitute a known-good BCM or reflash the BCM with the latest calibration before condemning it.
  7. Clear the code and verify the heated windshield activates and the wiper parks correctly through several key cycles before returning the vehicle.

Before you replace the wiper switch

  • A weak or failing battery or a recent jump start can set P1529 as a false request problem because the BCM logs the code when system voltage drops during a wiper or defrost request.
  • Water leaking past the cowl seal on many GM trucks and SUVs drips directly onto the wiper motor connector, corroding the request wire and setting P1529 without any switch failure.
  • An aftermarket remote start or alarm that taps the defrost request wire can back-feed voltage into the BCM and trigger P1529 even though the factory heated windshield circuit is intact.
  • The code does not always mean the heated windshield grid itself is bad; the BCM is reporting a request signal problem, so testing the grid resistance first often wastes time.
  • On some GM vehicles, a failing ignition switch or worn key cylinder can interrupt the accessory voltage that feeds the wiper switch, causing an intermittent P1529 that only appears when the key is wiggled.

Can I keep driving with P1529?

You can usually keep driving with P1529 because the heated windshield is a comfort and visibility feature, not a safety-critical system, but avoid relying on the defrost function in freezing conditions until it is repaired. If the wipers also misbehave in rain, treat the vehicle as having reduced visibility and get it checked promptly.

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.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage