BMW P0670: Glow Plug Control Module Control Circuit Malfunction — Diagnosis and Repair

P0670 means Glow Plug Control Module Control Circuit Malfunction. The DDE stores it when diesel glow-control module command and communication no longer matches the monitored operating state. Treat the record as a measured conclusion, then preserve glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state before clearing evidence or replacing a component. What Does P0670 Mean? P0670 is the standardized OBD-II definition for Glow Plug Control Module Control Circuit Malfunction. On a BMW, the decisive evidence comes from glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state. The code identifies the failed monitor, but it does not prove which individual wire, component, hydraulic path, or mechanical part caused that monitor to fail. P0670 concerns the control path between DDE and the glow module or the module's main supply. It is broader than a fault for one numbered glow plug. Confirm the installed engine, transmission, module, and wiring through the VIN before choosing a test point. Freeze-frame order matters because a supporting code recorded earlier can reveal whether this record is primary or only a consequence. Code: P0670 Definition: Glow Plug Control Module Control Circuit Malfunction Module: DDE Key data: glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state Typical cause: The glow-module power connector has heat damage or insufficient terminal tension under high current. Severity: condition dependent Note: confirm architecture and test points by VIN BMW P0670 marks a common glow-module control fault. Test loaded power, DDE communication, and cylinder currents during cold preheat. What Are the Symptoms of P0670? The measurable symptoms of P0670 must follow the behavior of diesel glow-control module command and communication, not a generic warning-lamp list. Compare the stored transition with a stable reference condition and look for a trace that changes late, stays fixed, drops out, or disagrees with its commanded state. These observations narrow the fault before parts are disturbed. • Glow-module status remains unavailable while the DDE requests preheating during a cold start. • All individual glow currents remain zero together, unlike a single-cylinder glow-plug failure. • Cold cranking lasts longer and white smoke appears briefly when combustion chambers receive no preheat. • Communication with the glow module drops as the engine-side harness warms or vibrates. • Main module voltage is absent even though individual glow-plug resistances are not simultaneously open. • The fault is strongest at low coolant temperature, when commanded glow duration and current are greatest. Why Does P0670 Occur? Causes of P0670 should be checked from accessible evidence toward expensive internal work. Begin with fluid level, connector condition, routing, shared supply, and component response that actually belong to diesel glow-control module command and communication. Escalate only when loaded electrical tests and live-data behavior exclude those paths; an expensive assembly is not the first diagnostic assumption. • The glow-module power connector has heat damage or insufficient terminal tension under high current. • A main fuse or fusible link opens after an overload in the glow system. • The DDE command or communication wire breaks where the engine harness bends. • Oil or water contamination enters the glow-control module connector. • The module's output electronics fail and stop responding to a valid DDE command. • DDE driver failure is considered only after module supply, ground, communication, and load pass. How Is P0670 Diagnosed with OBDThink? OBDThink is an independent BMW coding and diagnostics app and is not affiliated with BMW AG. Use OBDThink to preserve the P0670 freeze frame and graph glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state; this guide converts the evidence into a safe test order. • 1. Save coolant temperature, glow request, module state, every cylinder current, voltage, and communication faults. • 2. Verify that P0670 affects the common control path rather than only one glow-plug output. • 3. Inspect the glow-module connectors for heat discoloration, oil ingress, corrosion, and locking damage. • 4. Measure main supply and ground under commanded preheat load with a suitably rated method. • 5. Graph module status and individual currents from key-on through the complete cold-start glow period. • 6. Test the command or communication conductor while flexing its engine-side branch gently. • 7. Check glow plugs individually only after common module power and communication become trustworthy. • 8. Test the DDE output last with an approved load or BMW-directed communication procedure. IF the commanded state changes AND the measured diesel glow-control module command and communication trace stays fixed, THEN test the component connector under load. ELSE IF the trace changes at the connector but not at the DDE, THEN test the intervening harness. ELSE compare the physical response with glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state before authorizing an expensive repair. The fastest split is to graph glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state together; the first channel that stops agreeing determines the next physical test. How Is P0670 Repaired? Repair P0670 only after one test isolates the failed path in diesel glow-control module command and communication. Restore terminals, seals, routing, fluid condition, or wiring before replacing a sensor, valve, actuator, module, or mechanical assembly. After the work, repeat the original operating condition and compare the same data channels rather than accepting a cleared code as proof. • Low cost: clean and lock the glow-module connector after correcting fluid ingress. • Low cost: replace the failed fusible link only after locating the system overload. • Moderate cost: repair the broken DDE control or communication conductor in the engine harness. • Moderate cost: restore a heat-damaged main power terminal with the correct high-current repair. • High cost: replace the glow-control module when valid supply and command produce no response. • High cost: service DDE output circuitry only after a known-good module and wiring fail. After repair, confirm that P0670 no longer occurs, the original transition is stable, and the relevant monitor completes. Can You Drive with P0670? Driving with P0670 depends on the failure described by Glow Plug Control Module Control Circuit Malfunction. Use the stored data and current behavior to decide whether a short, gentle trip is defensible. Do not rely on the warning lamp alone: loss of lubrication, stalling, severe slip, fuel vapor, or unstable control requires a more conservative response. For P0670, base the trip decision on the code-specific trace and present vehicle behavior. Limit travel to diagnosis, avoid the recorded trigger, and stop if control, temperature, odor, noise, or warning severity changes. Short travel may be possible when warm, but repair before freezing conditions; stop for heavy smoke, severe misfire, electrical heat, or melted wiring. Which Questions Are Frequently Asked? Questions about P0670 should follow its own monitor evidence rather than a parts list. Preserve the first event, test the named data relationship, and repeat that exact condition after repair to prove the fault does not return. • Can P0670 clear by itself? P0670 identifies Glow Plug Control Module Control Circuit Malfunction. Diagnosis compares glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state so its electrical, control, and physical causes are separated before repair. • Should the named component be replaced first? No. Test its connector, supply, command, feedback, and physical response in the diesel glow-control module command and communication context before ordering a part. • How is the repair confirmed? Repeat the stored operating condition and verify that glow request, module status, individual glow current, coolant temperature, supply voltage, and communication state remain coherent. Confirm that P0670 no longer occurs and that its monitor completes without a new companion fault. Use the evidence chain from the first stored event to choose the next measurement for P0670. Once the repaired diesel glow-control module command and communication response matches its command through the original transition, document the final scan and keep that trace as the baseline for future diagnosis.