Common Causes of the TPMS Warning Light on SL CLASS Vehicles
The SL CLASS (a luxury sedan produced by Hongqi under FAW Group) uses a direct TPMS system. When the warning light stays solid or blinks, here are the most likely culprits:
- Dead sensor battery – No warning before failure. The battery is sealed inside the sensor and cannot be replaced.
- Valve stem corrosion – Aluminum or rubber stems crack, causing slow air loss and false low-pressure alerts.
- Signal interference – Aftermarket accessories (LED headlights, USB chargers, dashcams) operating in the 433MHz range can block sensor transmissions.
- Tire rotation or wheel change – Sensors are not automatically re-learned without a relearn procedure.
Dead Sensor Battery: Symptoms You Can’t Ignore
TPMS sensor batteries are non-replaceable and typically last 5–7 years. On SL CLASS models, these sensors are clamp-in style (valve stem attached to the sensor body).
Key symptoms of a dead battery:
- Warning light stays on for more than 10 minutes after driving.
- Cold weather triggers the light even when tire pressures are correct.
- One tire shows “—” or no pressure reading on the dashboard display.
- Intermittent warnings that disappear and reappear.
The BL-ST-046 (BH-Sens 433MHz) sensor is pre-programmed and works as a direct replacement. No cloning tool is needed for most SL CLASS years—just install and perform a relearn with a TPMS tool.
How to Diagnose Signal Interference
Signal interference is often overlooked. The 433MHz frequency is shared with many consumer electronics.
Common interference sources:
- Aftermarket LED license plate lights or interior lights with poor shielding
- Dashcams with wireless transmission modules
- Portable Bluetooth speakers or FM transmitters plugged into the 12V port
- Window tint with metallic film (acts as a Faraday cage)
Diagnosis steps:
- Turn off all aftermarket electronics one by one while monitoring the TPMS light.
- If the light goes out after disabling a device, that device is the interferer.
- Move the device farther from the wheel wells (e.g., relocate a dashcam from the windshield center to the rearview mirror area).
If the problem persists, the sensors themselves may have internal damage from road vibration or corrosion.
Fitment Comparison: BL-ST-046 vs. OE Sensor
| Feature | BL-ST-046 (BH-Sens) | OE 3778080HA01 |
|---|---|---|
| Frequency | 433MHz | 433MHz |
| Type | Clamp-in, pre-programmed | Clamp-in |
| Compatibility | Hongqi SL CLASS (multiple model years) | Hongqi specific |
| Weight | ~1 oz | ~1 oz |
| Programming | No cloning needed for most models | OE programmed |
| Warranty | 2-year standard | Varies by dealer |
Recommended Part
For a reliable replacement on your SL CLASS, use the BL-ST-046 | BH-Sens 433MHz TPMS Tire Pressure Sensor | Fits Hongqi | OE# 3778080HA01 (BH-Sens 433MHz, OE# 3778080HA01). It’s a clamp-in sensor that matches factory specifications and covers 2 vehicle applications from Hongqi.
FAQ
How do I know which TPMS sensor failed on my SL CLASS?
Use a TPMS diagnostic tool (like Autel or Bartec) to scan each sensor ID. The tool will show which sensor is missing or has a dead battery. Most tire shops can do this in 5 minutes for free.
Can I replace just one TPMS sensor, or should I do all four?
You can replace just the failed one, but if the others are over 5 years old, replace all four at once. You’ll save labor costs and avoid another warning light soon.
Will a dead TPMS sensor damage my tires?
Not directly, but the warning light means you might not know a tire is low. Driving on an underinflated tire causes heat buildup, tread wear, and potential blowout. Replace the sensor promptly.
Does the BL-ST-046 work with all SL CLASS model years?
It fits Hongqi vehicles using OE# 3778080HA01. Check your vehicle’s TPMS frequency (433MHz) and sensor type (clamp-in) before ordering. For years after 2020, verify with a compatibility chart or your VIN.