The Peterbilt 337 is a versatile medium-duty truck designed for vocational applications. Its instrument cluster provides critical real-time feedback to keep you safe and efficient. Understanding these indicators is essential for optimal performance and longevity.
Peterbilt 337 Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical system fault demands immediate attention in your Peterbilt 337; the truck should be stopped safely as soon as possible. | Pull over at the nearest safe location and shut down the engine; contact service. | |
| Master Caution | AMBER | A non-critical issue has been detected in your Peterbilt 337; it may be safe to continue but schedule a service check soon. | Monitor additional warning lights and consult your driver information display for details. | |
| Check Engine (MIL) | AMBER | The emissions control system or engine has detected a fault in your Peterbilt 337, which may reduce performance or fuel economy. | Have the system diagnosed by an authorized Peterbilt dealer at your earliest convenience. | |
| Engine Oil Pressure | RED | Low oil pressure in your Peterbilt 337's engine indicates a serious lubrication issue; continued operation can cause severe damage. | Stop the engine immediately, check oil level, and inspect for leaks; if level is OK, call for roadside assistance. | |
| Battery Charging | RED | The charging system in your Peterbilt 337 is not working properly, and the battery is discharging. | Check alternator belt tension and battery connections; if persistent, have the system tested. | |
| Coolant Temperature | RED | The engine coolant in your Peterbilt 337 has exceeded safe operating temperature, risking overheating. | Pull over safely, let the engine idle with heater on high to cool down; check coolant level and leaks. | |
| Transmission Temperature | AMBER | The transmission fluid in your Peterbilt 337 is hotter than normal; heavy load or low fluid may be the cause. | Reduce speed or downshift to ease load, and avoid prolonged heavy use until the temperature lowers. | |
| Brake System | RED | A hydraulic or air brake system fault has been detected in your Peterbilt 337, potentially reducing braking performance. | Do not drive; contact a service center to inspect brake fluid level, lines, and adjuster. | |
| ABS | AMBER | The anti-lock braking system on your Peterbilt 337 has a fault; normal braking is still available but ABS may not function. | Service the ABS as soon as possible; standard braking remains active. | |
| Parking Brake | RED | The parking brake is engaged on your Peterbilt 337; release it before moving. | Release the parking brake fully; if light stays on, check the brake switch or system. | |
| Tire Pressure (TPMS) | AMBER | One or more tires on your Peterbilt 337 are significantly underinflated, affecting handling and fuel economy. | Check and inflate all tires to the specified pressures shown on the driver's door placard. | |
| Seat Belt | RED | The driver's seat belt in your Peterbilt 337 is not fastened. | Fasten your seat belt immediately. | |
| Glow Plug / Preheat | AMBER | The glow plug system is active on your Peterbilt 337 to aid cold starts; wait for the light to go out before cranking. | Turn the key to the on position and wait until the light extinguishes, then start the engine. | |
| DPF / Regeneration | AMBER | The diesel particulate filter in your Peterbilt 337 is collecting soot and needs a regeneration cycle. | Drive at highway speeds or initiate a parked regeneration per the owner's manual. | |
| DEF / AdBlue | AMBER | The diesel exhaust fluid level is low in your Peterbilt 337; refill soon to avoid derate. | Add DEF/AdBlue at the next opportunity; consult your manual for the correct fluid type. | |
| Water in Fuel | AMBER | Water has been detected in the fuel system of your Peterbilt 337, which can damage the injectors. | Drain the water separator or have the fuel system serviced as soon as possible. | |
| Low Fuel | AMBER | Your Peterbilt 337 is running low on fuel; refill soon to avoid running out. | Refuel at the next station; do not let the tank run dry. | |
| High Beam | BLUE | The high beam headlights are activated on your Peterbilt 337. | Dim your high beams when approaching oncoming traffic. | |
| Power Steering (EPS) | RED | The electric power steering system in your Peterbilt 337 has a fault, causing heavy steering effort. | Stop safely and contact service; steering may still work but requires more effort. | |
| Reduced Power (Limp Mode) | AMBER | The engine control system has limited power output in your Peterbilt 337 to prevent damage. | Reduce speed and drive to a service center; the issue must be diagnosed. | |
| Air Filter | AMBER | The engine air filter on your Peterbilt 337 is restricted and needs replacement. | Replace the air filter according to the maintenance schedule. | |
| Fuel Filter / Water Separator | AMBER | The fuel filter or water separator on your Peterbilt 337 requires service or draining. | Replace the fuel filter and drain any water from the separator. | |
| Service / Hour Meter | GREEN | Your Peterbilt 337 has reached a scheduled maintenance interval based on engine hours. | Perform the required service as outlined in your owner's manual. | |
| Air Brake Pressure (Low) | RED | Air brake pressure in your Peterbilt 337 is below the safe threshold; braking may be compromised. | Do not drive; allow the compressor to build pressure; if persistent, check for leaks. | |
| Engine / Exhaust Brake | GREEN | The engine or exhaust brake is actively engaged on your Peterbilt 337, aiding deceleration. | Disengage the brake when not needed to avoid excess wear. | |
| Trailer | GREEN | A trailer is electrically connected to your Peterbilt 337, and its lights are functioning. | Verify trailer connection is secure before driving. | |
| Door Open | RED | A cab door on your Peterbilt 337 is not fully closed. | Check and securely close all doors. | |
| High Exhaust Temp (HEST) | AMBER | The exhaust system on your Peterbilt 337 is very hot during a regeneration cycle. | Avoid parking over flammable materials; the temperature will decrease after regeneration. | |
| Washer Fluid Low | AMBER | The windshield washer fluid level is low in your Peterbilt 337. | Top up the reservoir with approved washer fluid. |
29 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Check Engine Light (MIL) On
Common causes
- Faulty oxygen sensor
- Loose fuel cap
- Emissions system malfunction
What to do
For the Peterbilt 337, start by ensuring the fuel cap is tight. If the light persists, have the diagnostic trouble codes read by a Peterbilt dealer with Paccar software to pinpoint the issue.
Low Oil Pressure Warning
Common causes
- Insufficient engine oil level
- Oil pump failure
- Clogged oil filter
What to do
Immediately stop the Peterbilt 337 and check the oil dipstick. If low, add the recommended viscosity oil (e.g., 15W-40). If the level is fine but light remains, do not restart; tow to a shop.
Overheating Coolant
Common causes
- Coolant leak
- Thermostat stuck closed
- Radiator blockage
What to do
In the Peterbilt 337, pull over safely, let the engine idle with the heater on max heat to assist cooling. After cooldown, inspect coolant level and radiator for debris. If low, top up with approved coolant.
Brake System Failure
Common causes
- Low brake fluid
- Air in hydraulic lines
- Brake pad wear
What to do
For the Peterbilt 337, check the brake fluid reservoir. If low, add DOT 4 fluid and inspect for leaks. If the light remains, do not drive; have the brake system bled and inspected by a qualified technician.
Frequently Asked Questions
What does the red stop light with an exclamation mark mean on my Peterbilt 337?
That is the Master Warning (Stop) light, indicating a critical fault such as low oil pressure or brake failure. You must stop the vehicle safely and shut down the engine immediately.
How do I manually regenerate the DPF on my Peterbilt 337?
Park the truck in a well-ventilated area, ensure the transmission is in neutral and the parking brake is set. Then press the regen switch (usually on the dash) and follow the prompts on the driver display. The process takes about 20-30 minutes.
The Check Engine light is on, but the truck runs fine. Can I still drive?
You can drive short distances, but the light indicates a potential emissions or performance issue. Have the fault codes read soon to prevent further damage or derate. In your Peterbilt 337, it could be a simple sensor or a more serious problem.
Why does my brake warning light come on intermittently?
Intermittent brake warnings in the Peterbilt 337 often indicate low brake fluid or a failing brake switch. Check the fluid level first; if it's between min and max, the sensor may be faulty. Have it inspected to ensure safety.
The DPF light is flashing amber. What should I do?
A flashing amber DPF light means the filter is almost full and needs active regeneration. Drive at highway speeds (above 30 mph) for 20-30 minutes to allow passive regen. If it doesn't clear, initiate a parked regen as described in your manual.
How do I reset the service hour meter light on my Peterbilt 337?
The service light resets only after a dealer performs the required maintenance. However, you can clear the message from the display by holding the 'Set/Reset' button on the dashboard for 5 seconds, but the underlying interval will still need servicing.