What Does This Indicator Mean?
The Acura Yellow Glow Plug Warning Light is a specialized dashboard indicator found primarily on diesel-powered Acura vehicles (predominantly available in certain global markets). Unlike standard spark ignition systems, diesel engines rely on high heat generated by compression and electrical heating elements known as glow plugs to ignite diesel fuel within the combustion chambers, especially during cold starts. When this yellow indicator illuminates, it signals a fault within the diesel pre-heating system. The Engine Control Module (ECM) or Glow Plug Control Module continuously monitors the electrical resistance, voltage draw, and thermal output of the glow plugs. If the ECM detects out-of-range resistance, an open circuit, a blown relay fuse, or a communication failure across the glow plug circuit, it triggers this warning light to alert the driver of compromised combustion readiness.
Can I Still Drive with This Light On?
From a strict mechanical perspective, you can usually drive the vehicle short distances if the engine is already warm and running, but it is not recommended to ignore this warning. Because the yellow severity rating indicates a non-emergency yet urgent system fault, the primary immediate risk is severe difficulty or complete failure in starting the engine in lower ambient temperatures. Furthermore, modern diesel engines utilize glow plugs not just for initial startup, but also for post-heating phases to reduce emissions and ensure complete combustion. Driving with a failed glow plug system can cause rough idling, unburnt fuel washing down cylinder walls, excessive white smoke from the exhaust, and potential premature fouling or damage to the Diesel Particulate Filter (DPF) due to failed regeneration cycles.
Common Causes of the Warning
- Burnt-Out Glow Plug Heating Element: Over thousands of thermal cycles, the internal heating filament of one or more glow plugs can degrade, crack, or burn out entirely, creating an open electrical circuit that the ECM immediately flags.
- Faulty Glow Plug Control Module or Relay: A malfunctioning glow plug relay or dedicated control unit can fail to send the correct operating voltage and timing signals to the individual plugs, even if the plugs themselves are mechanically and electrically sound.
- High Resistance Caused by Carbon Buildup: Carbon deposits accumulating around the tip of the glow plug inside the combustion chamber can insulate the element, altering its thermal transfer properties and throwing off the electrical resistance parameters monitored by the ECM.
- Damaged Wiring Harness or Corrosion: Due to under-hood exposure to moisture, extreme heat, and road salt, the electrical wiring harness connecting the glow plug rail to the ECM can suffer from high resistance, frayed wires, or oxidized connector pins.
How to Diagnose and Reset It
Diagnosing the Acura Yellow Glow Plug Warning Light requires a methodical approach starting with specialized diagnostic tools. First, connect an OBD-II scanner capable of reading manufacturer-specific diesel powertrain trouble codes (DTCs) such as P0670 through P0674 to identify precisely which cylinder or control circuit has triggered the fault. Next, perform a manual physical inspection under the hood to check the glow plug wiring harness for secure connections, melted insulation, or corrosion. Use a digital multimeter set to ohms to test the electrical resistance of each individual glow plug by disconnecting the bus bar; a reading significantly out of standard manufacturer specifications indicates a failed plug that requires replacement. Once the faulty component—whether it is a glow plug, relay, or wiring harness—is replaced, clear the diagnostic trouble codes using your OBD-II scanner to reset the ECM and extinguish the warning light.