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P0616 and P0617: starter relay circuit low and high
A click and no crank sends most people to the starter motor. These codes point at the circuit that commands it, which is usually cheaper and easier to reach.
The starter motor draws hundreds of amps. Nothing in the ignition switch or the ECU handles current like that — a relay does, and often a heavy solenoid on the starter itself does the final switching.
P0616 and P0617 describe faults in the control path, not the motor.
| Code | Meaning |
|---|---|
| P0615 | Starter relay circuit malfunction |
| P0616 | Circuit low |
| P0617 | Circuit high |
Related: car won’t start diagnosis.
First: separate the three no-start symptoms
They point in completely different directions, and getting this right saves most of the work.
| What happens | Points at |
|---|---|
| Nothing at all, no click | Battery, relay, control circuit, immobiliser |
| Single loud click, no crank | Solenoid engaged, motor not turning, or low current |
| Rapid clicking | Battery too flat to hold the solenoid in |
| Cranks normally, does not fire | Fuel, spark or timing — not this article |
That last row matters: if the engine turns over properly, the starting system is working and the fault is elsewhere: engine cranks but won’t fire.
Rapid clicking is a battery symptom
Worth stating clearly because it is so commonly misread as a starter fault.
The solenoid pulls in, draws current, voltage collapses, the solenoid drops out, voltage recovers, and it pulls in again — several times per second. That is a battery that cannot deliver current, not a starter that has failed.
Test the battery under load before touching the starter.
How to jump start a car correctly and battery terminals corrosion.
Causes of the circuit codes
The relay
Cheapest and most common. Contacts pit from switching a heavy inductive load.
The swap test: find an identical relay in the same box — horn, air conditioning, fog lamps — and exchange them. If the fault follows the relay, done.
Fuses and relays basics for owners.
Fuses
The relay coil is fused, usually separately from the main feed. Test with a meter rather than by eye.
The neutral safety or clutch switch
The starter circuit is deliberately interrupted unless the transmission is in Park or Neutral, or the clutch pedal is fully down.
A worn or mis-adjusted switch means no crank at all, with a perfectly healthy starter. On an automatic, try starting in Neutral instead of Park — if it starts, the range switch is the fault: P0705 transmission range sensor.
On a manual, check that the clutch switch operates before the pedal reaches the floor.
The immobiliser
Many systems inhibit cranking, not just fuelling. A key not recognised produces a no-crank that looks electrical.
The tell: a security or key symbol on the dashboard. Car won’t start: immobiliser troubleshooting.
Wiring and grounds
The engine-to-body ground strap carries the starter’s return current. A corroded strap causes weak or no cranking and is easily overlooked because the fault is not near the starter.
The solenoid or motor
Last. Starters do fail — worn brushes, a burnt solenoid contact — but they fail after everything above in frequency.
The heat-soak version
A specific pattern worth recognising: the car starts fine cold, then refuses to crank after a short stop on a hot day, then starts again once it cools.
That is usually the starter solenoid contacts or the motor windings, both of which have higher resistance when hot. It is one of the few cases where the starter itself is the likely answer.
What the data adds
Log battery voltage during a crank attempt.
| Cranking voltage | Meaning |
|---|---|
| Stays above 10 V | Battery healthy, look at the circuit |
| Falls to 8–9 V | Battery weak or starter drawing excessively |
| Collapses to under 6 V | Battery flat or a dead short |
| Does not move at all | Nothing is being switched — control circuit |
That last row is the useful one for P0616. If voltage does not dip at all during the attempt, the starter never drew current, and the fault is upstream in the control path.
Sequence
- Identify the symptom — silence, single click, or rapid clicking.
- Test the battery under load.
- Try starting in Neutral on an automatic.
- Check for a security lamp on the dashboard.
- Swap the relay with an identical one.
- Check fuses with a meter.
- Inspect the ground straps.
- Then the starter.
Try it on the free tier of the app — pair an ELM327 adapter and log voltage during a failed crank attempt. Whether the voltage dips at all tells you which half of the system to investigate.
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