OBD-II Diagnostic Trouble Code
P0616 — Starter Relay Circuit Low
P0616 means the ECM saw the starter relay control circuit voltage lower than expected, which typically means the control wire is shorted to ground or the relay coil is shorted. The ECM can't properly switch the relay.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Starter Relay Circuit Low
Code
P0616
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Yes
What this means for truckers
P0616 (Starter Relay Low) — shorted to ground.
Before you replace parts — try this first
P0616 on the Ignition system is most often starter relay control wire chafed and shorted to ground — 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
No-crank or intermittent no-crank. In some designs a short to ground can energize the relay and the starter may engage unexpectedly, which is a safety concern. The check-engine light may come on.
Common causes
- CommonStarter relay control wire chafed and shorted to ground ($120–$450)
- CommonShorted starter relay coil ($40–$200)
- OccasionalWater or corrosion in the relay socket or connectors ($60–$250)
- RareFailed ECM driver ($1200–$3500)
How to fix
Measure the relay coil resistance against spec and replace the relay if it's low
When to use: First step
Pull the relay and check the control circuit for continuity to ground
When to use: To find a shorted wire
Repair the harness damage, often near the frame, starter or engine harness clips
When to use: When you find a short to ground
Clear the code and verify relay control during several crank cycles
When to use: After the repair
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
- → P0670 — Glow Plug Control Module Circuit
- → P0671 — Cylinder 1 Glow Plug Circuit
- → P0672 — Cylinder 2 Glow Plug Circuit
- → P0673 — Cylinder 3 Glow Plug Circuit
- → P0674 — Cylinder 4 Glow Plug Circuit
Frequently Asked Questions
Can I drive with code P0616?
P0616 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P0616 on a commercial truck?
Total repair cost ranges $40–$3500 depending on the root cause. The cheapest fix is usually the first one listed below — Starter relay control wire chafed and shorted to ground — 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 P0616 fail a DOT inspection?
P0616 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 P0616 and related codes?
P0616 is closely related to: P0670 (Glow Plug Control Module Circuit), P0671 (Cylinder 1 Glow Plug Circuit), P0672 (Cylinder 2 Glow Plug Circuit), P0673 (Cylinder 3 Glow Plug Circuit). These codes share the same subsystem (ignition) 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 P0616 is set without the companions, the issue is more isolated.
How do I prevent P0616 from coming back after a repair?
For P0616 (Starter Relay Circuit Low), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.