What this code means
P0615 may indicate that the ECM/PCM is seeing an unexpected condition in the starter cut relay diagnosis circuit.
What the vehicle may do
- The vehicle may have a no-crank or intermittent start concern.
- The code may store even if the starting concern is not present during the inspection.
Possible fault areas
- Possible fuse or relay circuit concern
- Possible connector or terminal issue
- Possible wiring issue between the relay box and ECM
- Possible ECM software or module-related issue after circuit checks pass
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, P0615 points us toward the ECM/PCM starter cut relay diagnosis circuit. In plain terms, the computer may not be seeing the starter cut relay circuit behave the way it expects. The vehicle may have a no-crank or intermittent start concern, or it may simply store the code. Broadly, we’re thinking about possible relay circuit issues, fuse power feed concerns, connector or terminal problems, wiring between the relay box and the ECM, or an ECM software or module path after the circuit checks out. Before jumping into pinpoint testing, start with the basic system checks and follow a structured diagnostic approach.
Duplicate the code first
Start by proving the fault is active. Select ON mode with the engine start/stop button, clear the DTC with the HDS, try to start the engine, then check the HDS again for pending or confirmed codes. If P0615 comes right back, the failure is duplicated and you move on. If P0615 does not return, treat it as intermittent for now. At that point, check for poor connections or loose terminals at starter cut relay 1, starter cut relay 2, and the ECM. If captured data is available for this code, try to reproduce the same conditions instead of guessing.
Sort out companion-code paths
Next, keep the code set in context. With the vehicle in ON mode, check the HDS for pending or confirmed codes. If the companion starter-control codes are present together, follow that diagnostic path first instead of continuing down the P0615 circuit check. If they are not present together, continue. Then select ON mode again, press the clutch pedal, and check pending or confirmed codes one more time. If the clutch-related companion code is present together with P0615, handle that diagnostic path first. If it is not, stay on the P0615 path and go to the fuse check.
Check the fuse before opening the circuit
Now turn the vehicle OFF and check the No. A5 (7.5 A) fuse in the under-hood fuse/relay box. If that fuse is OK, continue to the open-wire check. If it is not OK, replace the No. A5 (7.5 A) fuse, and also check for a short to ground on that fuse circuit. Don’t skip the short check, because a blown fuse without finding the reason can send you right back to the same failure.
Check the START_DIAG circuit for an open
With the fuse confirmed good, move to the START_DIAG and ST_RLY_1_TO_2 line. Remove starter cut relay 1 from the under-hood fuse/relay box, jump the SCS line with the HDS, and disconnect ECM connector A, the 49-pin connector. The test condition is OFF mode, starter cut relay 1 disconnected, and ECM connector A 49P disconnected. Check continuity between ECM connector A 49P terminal No. 24, the green wire, and starter cut relay 1 4P socket No. 2. If there is continuity, that wire is OK. If there is no continuity, repair the open in the START_DIAG/ST_RLY_1_TO_2 wire between ECM A24 and starter cut relay 1.
If the wire checks good
If the START_DIAG/ST_RLY_1_TO_2 wire has continuity, the circuit check has passed. At that point, update the ECM if it does not have the latest software, or substitute a known good ECM. If P0615 goes away after the ECM update, troubleshooting is complete. If P0615 goes away only with the known good ECM substituted, replace the original ECM.
Takeaway
The takeaway on P0615 is to duplicate the fault, separate out companion-code paths before circuit testing, check the No. A5 (7.5 A) fuse, then prove the START_DIAG/ST_RLY_1_TO_2 wire before moving into the ECM software or module decision. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0615 is often approached as an electrical circuit diagnosis: verify the code, handle companion-code context first, then check the fuse and starter cut relay diagnosis wire before considering the ECM.
For more guided automotive diagnostics, visit STEP Diagnostics.
