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DTC codes / GM codes / P1499

P1499 · GMOpen Or Shorted Condition Detected In The Hydraulic Cooling Fan Solenoid Control

P1499 on GM vehicles indicates that the powertrain control module has detected an open or shorted electrical condition in the control circuit for the hydraulic cooling fan solenoid. The computer monitors the solenoid's command wire for expected voltage or current and flags the code when the circuit falls outside the normal range, which prevents the hydraulic fan from being commanded properly.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the service engine soon or check engine light, often with no other noticeable symptoms
  • Engine cooling fan runs continuously at full speed or fails to run at all, leading to overheating in traffic
  • Coolant temperature gauge climbs higher than normal during idle or low-speed driving
  • Air conditioning performance degrades because the condenser fan assist is lost
  • Possible reduced engine power or limp mode if the PCM deems the fault severe enough to limit fan operation

Common causes, most likely first

  1. Broken, chafed, or corroded wiring in the hydraulic cooling fan solenoid control circuit, especially near the fan shroud or exhaust manifold
  2. Failed hydraulic cooling fan solenoid itself, either open coil or shorted internally
  3. Corroded or loose electrical connector at the solenoid or at the powertrain control module
  4. Blown fuse or damaged relay that supplies power to the solenoid control circuit
  5. Faulty powertrain control module driver for the solenoid control circuit, though this is less common
  6. Fluid contamination or mechanical binding in the hydraulic fan motor that overloads the solenoid circuit
  7. Aftermarket alarm or remote start wiring that has tapped into the fan control circuit and caused a short

How to diagnose and fix it

  1. Inspect the solenoid connector and the full run of the control wire for chafing, corrosion, or loose pins, repairing as needed
  2. Check the fuse and relay that feed the hydraulic fan solenoid circuit, replacing any that are blown or faulty
  3. Measure resistance across the solenoid coil and compare to the manufacturer's specification to confirm an open or short
  4. Back-probe the control wire at the PCM and command the fan on with a scan tool to verify the PCM is actually driving the circuit
  5. Perform a voltage drop test on both the power and ground sides of the solenoid circuit to locate hidden resistance
  6. Replace the hydraulic cooling fan solenoid if electrical tests confirm it is faulty, then clear the code and verify the fan operates through its full range
  7. If the circuit tests good but the code persists, check for a failed PCM driver before condemning the module

Hydraulic fan solenoid circuit traps to check first

  • A common oversight is assuming the solenoid is bad when the real problem is a chafed control wire behind the fan shroud or near the exhaust, so always trace the harness before replacing parts.
  • The hydraulic fan system uses a solenoid to vary fan speed, and a mechanical failure in the fan motor or a low fluid level can cause the solenoid to draw abnormal current and set P1499 even though the solenoid itself is fine.
  • Some technicians replace the PCM after finding a shorted control wire, but the short often damages the driver inside the PCM, so the module should be tested after any circuit repair.
  • This code can be set intermittently by water intrusion into the solenoid connector, so look for green corrosion or missing weather-pack seals even if the circuit tests good when dry.
  • A scan tool that can command the fan on and off is essential because a simple resistance check will not reveal a short that only occurs when the circuit is energized.

Can I keep driving with P1499?

You can drive short distances to a repair shop, but avoid heavy traffic, long idles, and towing because the hydraulic fan may not engage and the engine can overheat. If the temperature gauge rises above normal, pull over and shut the engine off immediately.

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.

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