The Kenworth T660's instrument cluster is designed for long-haul efficiency, featuring a centralized display that integrates critical warnings for engine, transmission, and aftertreatment systems. Its layout prioritizes visibility for the driver, with distinct color-coded alerts for immediate attention. This guide covers the essential warning lights and indicators unique to the T660.
Kenworth T660 Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical system failure has occurred in the T660 requiring immediate shutdown to prevent damage. | Safely pull over and shut down engine; refer to message center for specific fault. | |
| Master Caution | AMBER | A non-critical system warning is active on the T660, often accompanied by a message in the center display. | Check the message center and address the indicated issue at your earliest convenience. | |
| Check Engine (MIL) | AMBER | The T660's engine control module has detected a fault affecting emissions or performance, unique to PACCAR PX-9 or MX-13 engines. | Have the truck diagnosed with a PACCAR-approved scan tool as soon as possible. | |
| Engine Oil Pressure | RED | Engine oil pressure has dropped below safe levels in the T660, risking severe internal damage. | Stop immediately, check oil level, and inspect for leaks or pump failure. | |
| Battery / Charging | RED | The T660's charging system voltage is outside normal range, often due to alternator failure or loose belts. | Verify alternator belt tension and battery connections; if persistent, replace alternator. | |
| Coolant Temperature | RED | Engine coolant temperature has exceeded the safe maximum for the T660, indicating potential overheating. | Pull over, idle the T660 to cool, and check coolant level and fan operation. | |
| Transmission Temp | AMBER | Transmission fluid temperature in the T660 is above normal, often due to heavy load or low fluid. | Reduce load and monitor; if light stays on, service transmission and check fluid level. | |
| Brake System | RED | A fault in the T660's primary brake system, such as low air pressure or brake circuit failure, has been detected. | Do not drive; check air brake pressure and inspect brake components. | |
| ABS | AMBER | The T660's anti-lock braking system has a malfunction; standard brakes function but ABS is disabled. | Have the ABS system inspected at a Kenworth dealer soon. | |
| Parking Brake | RED | The parking brake on the T660 is engaged or not fully released. | Release the yellow knob fully before moving the truck. | |
| Tire Pressure (TPMS) | AMBER | One or more tires on the T660 are significantly under-inflated, affecting fuel economy and safety. | Check all tire pressures and inflate to the recommended PSI listed on the door placard. | |
| Seat Belt | RED | The driver's seat belt in the T660 is not fastened. | Fasten the seat belt immediately for safety compliance. | |
| Glow Plug / Preheat | AMBER | Glow plugs are active on the T660 for cold start preheating, typical with PACCAR MX engines. | Wait for the light to turn off before cranking the engine. | |
| DPF / Regeneration | AMBER | The T660's diesel particulate filter is reaching soot limit and has initiated active regeneration. | Drive at highway speeds above 30 mph to allow the regeneration process to complete. | |
| DEF / AdBlue | AMBER | Diesel Exhaust Fluid level is low or quality is poor in the T660, which can limit engine power. | Refill the DEF tank with approved fluid; if quality issue, drain and replace. | |
| Water in Fuel | AMBER | Water has been detected in the T660's fuel filter/separator, risking injector damage. | Drain the water separator immediately; replace filter if necessary. | |
| Low Fuel | AMBER | The T660's fuel level is low, with approximately 20 gallons remaining. | Refuel as soon as possible to avoid running out on the road. | |
| High Beam | BLUE | High beam headlights are on in the T660, providing maximum forward illumination. | Dim lights when approaching oncoming traffic to avoid blinding others. | |
| Air Brake Pressure (Low) | RED | Air brake system pressure in the T660 has dropped below 60 psi, making brakes unsafe. | Stop immediately; do not drive until pressure is restored and warning clears. | |
| Engine / Exhaust Brake | GREEN | The T660's engine brake or exhaust brake is active and assisting deceleration. | Normal operation; the brake engages automatically when switch is on and throttle is released. | |
| Trailer | AMBER | A fault with the trailer connection or trailer ABS has been detected on the T660. | Check trailer electrical plug, brake connections, and trailer ABS status. |
21 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Check Engine (MIL) - Persistent
Common causes
- Faulty EGR valve or sensor
- Diesel particulate filter restriction
- Turbocharger boost sensor issue
What to do
Use a PACCAR diagnostic tool to read codes; for the T660, common fixes include cleaning EGR, forced DPF regeneration, or replacing boost sensor.
Engine Oil Pressure Low
Common causes
- Low oil level due to consumption or leak
- Oil pump failure or worn bearings
- Clogged oil filter
What to do
Check oil level and add if needed; if level is fine but light remains, the T660 should be towed to a shop for oil pressure testing and possible pump replacement.
Coolant Temperature Overheating
Common causes
- Low coolant level from leak
- Thermostat stuck closed
- Radiator fan clutch failure
What to do
Let the T660 idle to cool, then check coolant level and hoses for leaks; if no leak, inspect fan clutch operation and replace thermostat if stuck.
Brake System Air Pressure Low
Common causes
- Air leak in brake lines or chambers
- Failed air compressor or governor
- Excessive brake use draining supply
What to do
Locate and repair air leaks; if compressor is at fault, the T660 needs professional compressor replacement; avoid driving until pressure is stable above 100 psi.
DPF Regeneration Inhibited
Common causes
- Frequent short trips preventing regen
- Faulty exhaust temperature sensor
- Clogged DPF beyond automated regen
What to do
Drive the T660 at highway speeds for 20-30 minutes to enable passive regen; if light persists, a forced stationary regen at a Kenworth dealer is required.
Frequently Asked Questions
What does the DPF Regen light mean on my Kenworth T660?
The DPF regen light indicates the diesel particulate filter is accumulating soot and has started active regeneration. To help it clear, drive the T660 at highway speeds (above 30 mph) for 20-30 minutes. If the light stays on, the filter may need a forced regeneration at a dealer.
Why is the Check Engine light on, but the T660 runs fine?
On the T660, the check engine light often signals an emissions-related fault, such as a loose fuel cap, EGR valve issue, or sensor drift. Even if performance seems normal, have the codes read with a PACCAR tool to prevent future problems or reduced power.
How do I reset the service maintenance light on my T660?
The service maintenance light (hour meter) resets via the dash display menu. Navigate to 'Maintenance' settings, select 'Reset Service' and confirm. If it doesn't reset, a dealer can manually reset it after completing the required service.
What does the Air Brake Light mean when I first start the T660?
The air brake light on startup is normal if pressure is below 100 psi. Let the air compressor build pressure until the light goes out (typically above 120 psi). If it stays on, check for air leaks or a faulty governor.
Can I ignore the Water in Fuel light briefly?
No. The Water in Fuel light means moisture has collected in the fuel/water separator. Ignoring it can allow water into the injectors, causing expensive damage on the T660's PACCAR engine. Drain the separator immediately using the valve at the bottom of the filter.
Why does my T660's DEF light come on even after refilling?
If the DEF light stays on after refilling, the system may need to be primed or the DEF quality sensor may have detected improper fluid. Drive a few miles; if it remains, have the sensor checked—using non-approved DEF is a common cause.