What Does This Indicator Mean?
The Great Wall Yellow Glow Plug Warning Light is a specialized dashboard indicator found exclusively on Great Wall diesel-powered vehicles, such as the Steed and Poer series. In a diesel engine, fuel ignition relies entirely on the heat of compression rather than an electric spark. Because a cold engine block absorbs this heat and prevents proper combustion, diesel engines use heating elements known as glow plugs to pre-warm the combustion chambers prior to startup, as well as post-heat them to stabilize idle quality. When this yellow icon illuminates, the Engine Control Module (ECM) has detected an electrical, thermal, or mechanical fault within the pre-heating subsystem. The ECM constantly monitors the resistance, current draw, and continuity of each individual glow plug, the glow plug control module, and the associated wiring harness. If a discrepancy falls outside factory-calibrated thresholds—such as an open circuit in a heating element or a delayed warm-up cycle—the ECM flags the fault code and triggers this warning light on your instrument cluster.
Can I Still Drive with This Light On?
The short answer is yes, but with significant caveats depending on ambient temperatures and engine status. Because the severity color is yellow, it indicates a non-critical emissions or auxiliary system fault rather than an immediate catastrophic engine failure. If the vehicle is already at operating temperature, you can usually drive it safely to a service facility. However, if you are attempting a cold start in low ambient temperatures, a compromised glow plug system will make ignition extremely difficult, leading to extended cranking times, rough idling, dense white unburnt diesel smoke from the exhaust, and potential fuel wash down of the cylinder walls. Continuing to drive indefinitely with this light illuminated can also lead to incomplete DPF (Diesel Particulate Filter) regeneration cycles, because many modern Great Wall diesels utilize the glow plugs to elevate exhaust gas temperatures during active regeneration events.
Common Causes of the Warning
- Burnt-Out Glow Plug Heating Element: Over thousands of thermal cycles, the internal resistance wire inside one or more glow plugs can degrade, crack, or completely fracture, resulting in an open circuit that prevents proper electrical heating.
- Faulty Glow Plug Control Relay or Module: The solid-state relay or dedicated control module responsible for switching high current to the glow plugs based on ECM commands can suffer internal component failure, cutting power to the plugs entirely.
- High-Resistance Wiring and Connector Corrosion: Due to the harsh thermal and moisture-prone environment of the engine bay, the electrical harness, ground points, and heavy-gauge terminal pins connecting to the glow plugs can develop high resistance or corrosion, confusing the ECM current sensors.
How to Diagnose and Reset It
Diagnosing the Great Wall Yellow Glow Plug Warning Light requires a systematic approach using both electronic diagnostic tools and basic physical testing. First, connect an OBD2 diagnostic scanner capable of reading manufacturer-specific diesel powertrain codes to the vehicle’s data link connector under the dashboard. Look for diagnostic trouble codes starting with prefix P0670 through P0674, which directly point to glow plug control circuit malfunctions or individual cylinder glow plug faults. If a specific cylinder is flagged, pop the hood and use a digital multimeter set to ohms to test the resistance of each glow plug directly at its terminal. A healthy metallic glow plug typically exhibits very low resistance, whereas a failed unit will show infinite resistance (open circuit). Inspect the wiring harness and relay for loose pins or corrosion. Once you replace the faulty glow plug, control module, or repair the damaged wiring, clear the trouble codes using your OBD2 scanner to reset the warning light. If the underlying mechanical or electrical fault has been fully resolved, the warning light will remain off upon subsequent vehicle startup.