OBD-II Diagnostic Trouble Code
U0106 — Lost Communication With Glow Plug Control Module
U0106 indicates the ECM lost communication with the glow plug control module, which manages preheat on diesel engines that use glow plugs. The ECM cannot command or monitor glow plugs. The module may have lost power, ground or its communication link; many heavy diesels use an intake grid heater instead and will not set this code.
Severity 2/5
Truck-relevant
Service soon
Severity
Service soon
Lost Communication With Glow Plug Control Module
Code
U0106
Category
Network
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
U0106 (Lost Communication With Glow Plug Control Module) — GPCM offline. Cold-weather starts will be hard.
Before you replace parts — try this first
U0106 on the Network system is most often corroded or loose connector at the glow plug module, often exposed under the hood or on the frame — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Hard starting in cold weather, white smoke and rough idle after a cold start, and a glow plug or check-engine light. Warm-engine operation is usually normal.
Common causes
- CommonCorroded or loose connector at the glow plug module, often exposed under the hood or on the frame ($100–$400)
- CommonBlown fuse or poor ground for the module ($50–$250)
- OccasionalFailed glow plug control module ($250–$800)
- OccasionalDamaged communication wire between ECM and module ($150–$500)
How to fix
Check module fuse, power feed and ground
When to use: First step
Clean and inspect the module connector and wiring
When to use: When corrosion or water exposure is present
Replace the glow plug control module
When to use: When power, ground and wiring are good but it will not communicate
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → U0100 — Lost Communication With ECM/PCM A
- → U0101 — Lost Communication With TCM
- → U0102 — Lost Communication With Transfer Case Control Module
- → U0103 — Lost Communication With Gear Shift Module
- → U0104 — Lost Communication With Cruise Control Module
Frequently Asked Questions
Can I drive with code U0106?
U0106 is severity 2 — service this week. Not an immediate stop, but ignoring it usually compounds the problem. Most common cause for this code is a worn sensor or minor performance fault that won't strand you today but will get more expensive the longer you wait.
How much does it cost to fix U0106 on a commercial truck?
Total repair cost ranges $50–$800 depending on the root cause. The cheapest fix is usually the first one listed below — Corroded or loose connector at the glow plug module, often exposed under the hood or on the frame — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will U0106 fail a DOT inspection?
U0106 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between U0106 and related codes?
U0106 is closely related to: U0100 (Lost Communication With ECM/PCM A), U0101 (Lost Communication With TCM), U0102 (Lost Communication With Transfer Case Control Module), U0103 (Lost Communication With Gear Shift Module). These codes share the same subsystem (network) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only U0106 is set without the companions, the issue is more isolated.
How do I prevent U0106 from coming back after a repair?
For U0106 (Lost Communication With Glow Plug Control Module), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.