P0616

What it means

P0616 is a generic powertrain code meaning the control unit has detected a low voltage or low signal in the control circuit for starter relay A. The module commands the relay and monitors the circuit, and it set the code when the voltage it saw did not match the commanded state, pointing to a short to ground, an open circuit or a fault in the relay or its driver.

Symptoms

• Engine cranks slowly, intermittently or not at all
• Engine does not crank when the key or start button is operated, although the dash lights come on
• Starter keeps running or clicks without cranking
• Intermittent no-start that comes and goes with temperature or vibration
• Engine management or check engine light on
• Start-stop system not working or restarts failing

Possible causes

• Faulty starter relay (internal contacts or coil failing)likely
• Corroded, loose or damaged connector or terminals at the relay or relay boxlikely
• Wiring in the relay control circuit shorted to ground or chafed throughpossible
• Low battery voltage or poor battery and earth connections causing the control circuit to read lowpossible
• Fault in the ignition switch, start button or immobiliser or body control signal that feeds the start requestpossible
• Internal driver fault in the engine control unit or the module that controls the relayrare

How to diagnose

1. Read all stored and pending codes and freeze frame data, noting battery voltage and conditions when the code set, then check for related battery, immobiliser or communication codes
2. Test the battery state of charge and check the battery terminals and main earth straps for tightness and corrosion
3. Inspect the starter relay, its socket and connector for water ingress, heat damage, green corrosion or bent terminals
4. Swap the relay with a known good identical one, if the vehicle layout allows, and see whether the fault follows the relay
5. Check the relay fuse and the supply feed to the relay with a multimeter, following the wiring diagram for that model
6. Back-probe the control circuit while a start is requested and check for the commanded voltage change; look for a short to ground by checking resistance to earth with the connector disconnected
7. Check the wiring loom between the control unit and relay for chafing, particularly at bulkhead grommets and moving points
8. If the circuit and relay are good, check the start request inputs and the control unit output, and confirm against manufacturer data for that model

How to fix

• Replace the faulty starter relay with the correct specification part
• Clean or repair corroded terminals and replace damaged connectors or the relay socket
• Repair or replace shorted or chafed wiring in the relay control circuit
• Recharge or replace the battery and restore clean, tight battery and earth connections
• Repair or replace a faulty ignition switch, start button or related module input
• Repair or replace the control unit only after wiring, relay and inputs are proven good, and carry out any programming required

Can I keep driving?

Nearby codes

• P0615GenericStarter Relay A Circuit
• P0617GenericStarter Relay A Circuit High