The Volvo Trucks WG, a robust vocational model from the late 1990s and 2000s, features a straightforward instrument cluster with warning lights for engine, brakes, and chassis systems. This guide covers the essential indicators you'll see on the WG's dashboard.
Volvo Trucks WG Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | On the Volvo WG, this red stop light means a critical failure has occurred—often tied to low oil pressure or high coolant temp—and demands immediate shutdown to prevent engine damage. | Stop engine safely and check fault codes or consult manual. | |
| Master Caution | AMBER | The amber caution light on your WG indicates a non-critical fault that still needs attention, such as a minor sensor issue or pending service reminder. | Check other warning lights and schedule service soon. | |
| Check Engine (MIL) | AMBER | Illuminated when the Volvo WG's ECU detects an emission or performance fault—common causes include a faulty EGR or injector issue. | Have the engine scanned with Volvo diagnostics to identify the trouble code. | |
| Engine Oil Pressure | RED | This red light on the WG warns of dangerously low oil pressure, which can starve bearings and lead to catastrophic engine failure if ignored. | Shut down immediately, check oil level, and do not restart until pressure is restored. | |
| Battery / Charging | RED | When the battery light stays on in your WG, it signals the alternator is not charging the battery—often due to a broken belt or failed alternator. | Check belt tension and alternator output; replace as needed to avoid being stranded. | |
| Coolant Temperature | RED | The WG's coolant temp light glows red when the engine is overheating, typically from a stuck thermostat, low coolant, or a failing fan clutch. | Stop engine, let it cool, check coolant level and fan operation; have the cooling system inspected. | |
| Transmission Temp | RED | On your WG, a red transmission temp light means the gearbox oil is too hot—often from heavy hauling or low fluid—and could cause transmission damage. | Stop and let transmission cool; check fluid level and condition; reduce load or have cooler checked. | |
| Brake System | RED | This red light on the Volvo WG indicates a brake system pressure fault, such as low air pressure or a leak, compromising braking ability. | Do not drive; inspect for air leaks and verify brake pressure builds before moving. | |
| ABS | AMBER | The amber ABS light on your WG means the anti-lock system has a fault, often a wheel speed sensor issue, but normal brakes still work. | Drive cautiously and have the ABS system diagnosed; avoid hard braking on slippery roads. | |
| Parking Brake | RED | When the parking brake light stays on in the WG, it either indicates the brake is engaged or there's a low air pressure condition preventing release. | Ensure brake is fully disengaged; if light stays on, check air pressure and spring brake valve. | |
| Seat Belt | RED | The seat belt reminder on the WG illuminates when the driver's belt is unbuckled while the ignition is on—a basic safety nudge. | Buckle your seat belt to extinguish the light. | |
| Glow Plug / Preheat | AMBER | In the WG with a diesel engine, this light stays on longer than usual when glow plugs are failing or the preheat system has a fault, making cold starts harder. | If light stays on for more than 10 seconds, have glow plugs and relay tested. | |
| Water in Fuel | AMBER | This amber light on the WG warns that water has accumulated in the fuel filter/water separator, which can damage the injection system if not drained. | Drain the water separator immediately; if light persists, replace the fuel filter. | |
| Low Fuel | AMBER | The low fuel light on your WG comes on when the tank level drops below roughly 10% capacity, giving you time to find a diesel station. | Refuel as soon as possible to avoid running out and drawing air into the fuel system. | |
| High Beam | BLUE | A blue high beam indicator confirms the WG's headlights are in high-beam mode, providing maximum road illumination. | Dim to low beam when approaching oncoming traffic to avoid glare. | |
| Power Steering (EPS) | AMBER | On the WG, an amber power steering light indicates low fluid pressure or a pump fault, leading to heavier steering effort. | Check power steering fluid level and belt; if low, top up and inspect for leaks. | |
| Reduced Power (Limp Mode) | AMBER | When this light appears on your WG, the engine ECU has entered limp mode to protect against damage—typically from a turbo or fuel system issue. | Reduce speed and have the vehicle towed to a shop for diagnostic scanning. | |
| Air Filter | AMBER | This amber light on the WG signals that the engine air filter is clogged, restricting airflow and reducing power and fuel efficiency. | Replace the air filter and check the intake system for blockages. | |
| Fuel Filter / Water Separator | AMBER | On the WG, the fuel filter light indicates the filter is clogged or has reached its service interval, which can cause starting and performance issues. | Replace the fuel filter and prime the system per Volvo procedure. | |
| Service / Hour Meter | AMBER | The service light on your WG illuminates when the engine hour meter reaches the preset interval for oil change and general maintenance. | Schedule service soon; reset the maintenance minder after completion. | |
| Work Lights | GREEN | A green work light indicator on the WG shows that auxiliary work lights on the cab are activated, improving visibility around the truck. | Turn off work lights when not needed to avoid battery drain. | |
| Beacon / Rotating Light | GREEN | On the WG, this green light means the amber beacon on the roof is on, required for visibility in construction zones or low-speed operations. | Check that the beacon is not obstructed; turn off when not on a job site. | |
| Differential Lock | AMBER | The diff lock indicator on your WG tells you the rear axle differential is engaged, providing maximum traction on slippery surfaces. | Disengage diff lock when on dry pavement to prevent driveline binding. | |
| PTO Engaged | GREEN | The green PTO light on the WG confirms the power take-off is engaged, running auxiliary equipment like a dump body or winch. | Ensure all personnel are clear before operating PTO; disengage when not in use. | |
| Air Brake Pressure (Low) | RED | On the WG, a red low air brake pressure light warns that the reservoir pressure is below 60 psi, making safe braking impossible. | Do not drive; wait for pressure to build or check for air leaks in the system. | |
| Engine / Exhaust Brake | GREEN | A green retarder indicator on the WG shows that the engine brake or exhaust brake is active, assisting downhill speed control. | Use retarder wisely to avoid over-revving; disengage if the road becomes icy. | |
| Trailer | AMBER | The amber trailer light on your WG illuminates when there is a fault in the trailer's electrical connection, such as a short or disconnected plug. | Check the trailer wiring and connector; repair as needed to restore lights/brakes. | |
| Door Open | RED | When the door-open light is on in the WG, it indicates the driver's door is ajar while the ignition is on—a simple safety reminder. | Close the door securely to extinguish the light. | |
| Low Oil Level | AMBER | This amber light on the WG warns that engine oil level is low, which can lead to pressure drops if not topped up soon. | Check oil level on dipstick and add recommended grade oil to full mark. | |
| Brake Fluid Level | RED | On the WG, a red brake fluid light indicates the master cylinder reservoir is low, often due to worn brake pads or a leak. | Check fluid level and condition; inspect brake system for leaks; have pads checked. | |
| High Exhaust Temp (HEST) | AMBER | The amber exhaust temp light on the WG warns that the exhaust or turbo temperatures are high, often during a regeneration or heavy load operation. | Reduce engine load and allow the system to cool; avoid parking over dry grass. |
31 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Engine Oil Pressure Loss
Common causes
- Oil leak
- Faulty oil pump
- Clogged oil filter
What to do
Shut down engine immediately. On the Volvo WG, check oil level and inspect for major leaks. If oil is full, have pressure sensor and oil pump tested at a Volvo shop.
Overheating Engine
Common causes
- Low coolant
- Broken fan belt
- Stuck thermostat
What to do
Stop the WG and let it cool. Check coolant level and top up with recommended fluid. Inspect fan belt tension and replace if loose.
Air Brake System Failure
Common causes
- Air leak in lines
- Failed compressor
- Brake valve issue
What to do
Do not drive. On the WG, listen for air leaks around brake chambers and lines. If compressor won't build pressure, check drive belt and unloader valve.
Alternator Failure
Common causes
- Broken serpentine belt
- Worn brushes
- Short circuit
What to do
Check belt tension and condition on the WG. If belt is fine, test alternator output; replace alternator if not charging properly.
Transmission Overheating
Common causes
- Low transmission fluid
- Overloaded vehicle
- Faulty cooler
What to do
Pull over and let transmission cool on the WG. Check fluid level with engine idling; if low, add correct fluid. Have cooling system inspected for blockages.
Frequently Asked Questions
Why does my WG's check engine light stay on after starting?
On the WG, the MIL stays on if the ECU detected a persistent fault like a failed DPF pressure sensor or EGR valve issue. Have the codes read with Volvo's diagnostic tool to pinpoint the problem.
What should I do if the brake system light comes on while driving?
Stop immediately. On the WG, a red brake light means low air pressure—wait for pressure to build. If it doesn't, check for air leaks around the treadle valve or quick-release valves.
Why is my WG's fuel filter light on after I just changed the filter?
The sensor may still see air or water if the filter wasn't primed correctly. On the WG, try priming the fuel system by cycling the key several times or using the lift pump.
How often should I service the air filter on my WG?
The WG's air filter should be replaced every 30,000 miles or when the restriction indicator shows red. In dusty conditions, more frequent checks are needed.
What does the glow plug light staying on for 20 seconds mean?
On the WG, a prolonged glow plug light indicates a failed heating element or relay. Have the glow plugs tested with a multimeter or diagnostic scanner.
Can I drive with the ABS light on in my Volvo WG?
Yes, normal brakes work but ABS is disabled. On the WG, drive cautiously, especially on wet roads, and have the ABS sensor and module checked soon.