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DTC codes / P06xx · Computer and output circuits / P0616

P0616Starter Relay Circuit Low

P0616 means the powertrain control module (PCM) has detected a low-voltage condition on the starter relay control circuit, which is the wire the PCM uses to command the relay that engages the starter. The PCM expects to see a voltage near battery level when the relay is not commanded and near ground when it is, and a persistent low reading tells it the circuit is shorted to ground or the relay coil has failed.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • The engine may not crank at all when you turn the key or press the start button
  • A single click or rapid clicking from the starter relay area when starting is attempted
  • The check engine light (malfunction indicator lamp) is illuminated on the dashboard
  • The starter may crank normally in some conditions, especially when the circuit is intermittent
  • Often no symptoms besides the warning light, with the vehicle starting and running normally
  • In some vehicles the PCM may disable the starter circuit as a protective measure, leaving you stranded

Common causes, most likely first

  1. A short to ground in the starter relay control wire between the PCM and the relay
  2. A failed starter relay with an open or shorted coil winding
  3. Corroded, loose, or damaged relay socket terminals or connector pins
  4. A faulty PCM driver circuit for the starter relay, often caused by water intrusion or internal damage
  5. Rodent damage or chafing of the wire harness along the starter relay circuit
  6. A poor ground connection at the relay or at the PCM, causing a false low-voltage reading

How to diagnose and fix it

  1. Scan all modules for stored codes and record freeze-frame data to confirm P0616 is current and not history
  2. Inspect the starter relay and its socket for corrosion, loose pins, and signs of overheating, then swap the relay with an identical known-good relay to test
  3. Disconnect the PCM connector and the relay, then measure resistance from the control wire to ground to check for a short
  4. Check the control wire for continuity and voltage drop from the PCM to the relay while wiggling the harness to reveal intermittent faults
  5. Verify the relay coil resistance and confirm the PCM is commanding the relay by back-probing the control circuit during a crank request
  6. If the circuit and relay test good, check the PCM ground and power feeds before condemning the PCM
  7. Replace the faulty relay, repair the shorted wire, or replace the PCM only after all other tests pass

What the starter relay circuit test misses

  • A relay that clicks does not prove the coil is good, because a partially shorted coil can still pull in the armature while drawing too much current and setting a low-circuit code
  • The PCM may set P0616 when the ignition switch is left in the start position too long, so check for a sticking ignition switch or a start button that stays engaged
  • Water intrusion into the underhood fuse box or PCM connector is a common hidden cause that a simple relay swap will not fix
  • Some vehicles use a starter relay integrated into the body control module (BCM) or a smart junction box, so the control wire may not run directly to the PCM
  • A weak battery or bad engine ground can cause a low-voltage spike on the control circuit that mimics a short, so always load-test the battery first

Can I keep driving with P0616?

If the engine still cranks and runs normally, you can drive to a repair shop, but avoid repeated long crank attempts that could overheat the starter. If the engine will not crank at all, do not keep trying, because you risk damaging the starter or relay further, and have the vehicle towed or repaired on site.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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