What this code means
P1659 may indicate an electronic throttle control system relay OFF malfunction, where the PCM can be commanding the PGM-FI subrelay on but may not see the expected power supply on.
What the vehicle may do
- The vehicle may turn on a warning light.
- Throttle response may be reduced or limited.
- The vehicle may have drivability symptoms depending on how the fault is present.
Possible fault areas
- Possible relay power supply circuit issue.
- Possible relay control or relay output wiring issue.
- Possible short-to-ground condition.
- Possible connector or terminal concern.
- The PCM may be involved after the related circuit checks are normal.
Diagnostic path
Open and code meaning
Today we’re diagnosing P1659 on a 2017 to 2025 Honda CR-V with the 1.5 turbo. In plain terms, this code points to an electronic throttle control system relay OFF malfunction. The PCM may be commanding the PGM-FI subrelay on, but it is not seeing the expected power supply input. On the vehicle, this can show up as reduced throttle response, a warning light, or other drivability limits. The broad fault areas are the relay power feed, the relay control and output wiring, a possible short to ground, connector issues, and only after the circuit checks pass, the PCM itself. Start with the basic system checks first, and if other codes are present, understand those before getting too deep into this one.
Confirmation and first power check
To begin the confirmation path, turn the vehicle to ON mode. From there, start the plus B DBW circuit inspection with the PGM-FI subrelay disconnected. This is the first split in the diagnosis: you’re checking whether the DBW power supply side is where it should be. Both listed plus B DBW checks are done with IG Mode OFF, and each normal result is 12 V battery voltage. If either check is abnormal, treat that as a circuit problem, then continue into the additional power supply inspection to narrow down where the failure is.
Open circuit checks
Next, move into the FI_SUB_RLY_CL- and FI_SUB_RLY_OUT open wire checks. Before disconnecting the PCM connector, jump the SCS line with the HDS and wait more than 1 minute. Then disconnect the PGM-FI subrelay and PCM connector A, the 50P connector. With IG Mode OFF, check the FI_SUB_RLY_CL- circuit and the FI_SUB_RLY_OUT circuit. Each one should measure less than 1 Ω. If either one is abnormal, the diagnostic direction stays in the wiring circuit, not the PCM.
Short-to-ground check
If the open checks pass, move to the FI_SUB_RLY_OUT shorted wire inspection. Again, before disconnecting the PCM connector, jump the SCS line with the HDS and wait more than 1 minute. For this check, the PGM-FI subrelay is disconnected, PCM connector A, the 50P connector, is disconnected, and the related loads on that output side are unplugged, including the fan relay circuits, purge valve, air fuel sensor, and the leak check module on USA and Canada models. Use the proper open and short checking method for the circuit, and do not guess at terminal locations. With IG Mode OFF, the FI_SUB_RLY_OUT short-to-ground check should show more than 1 MΩ. If it is abnormal, there is a circuit problem.
PCM conclusion and close
Only after the other inspection items show normal results does the path point to the remaining PCM as the cause. So the order matters here: confirm the code path, check the plus B DBW power supply, check the relay control and output circuits for opens, check FI_SUB_RLY_OUT for a short to ground, and only then make the PCM call. The takeaway: P1659 is a power supply and relay circuit diagnosis first, not a parts-swap diagnosis. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often approached as a relay power supply and circuit integrity diagnosis before considering the PCM.
For more guided automotive diagnostics, visit STEP Diagnostics.
