What this code means
P1659 may set when the PCM commands the electronic throttle related relay circuit on but does not see the expected power supply input.
What the vehicle may do
- The vehicle may store a warning light or throttle system fault.
- Throttle response may be limited or reduced in some cases.
- The code can also be present with few obvious drivability symptoms.
Possible fault areas
- Possible relay power feed or relay socket circuit issue.
- Possible open in the relay control or output wiring.
- Possible short to ground in the relay output circuit.
- Possible connector, terminal, or harness issue.
- Possible PCM-related fault after the circuit checks are normal.
Diagnostic path
Opening context
On this 2020 to 2025 Honda CR-V hybrid, P1659 points to an electronic throttle control relay OFF malfunction. In plain terms, the PCM is commanding the PGM-FI subrelay on, but it is not seeing the power supply input it expects. The vehicle may have throttle control concerns, reduced response, a warning light, or it may simply store the code. Broadly, this can involve relay power feed issues, an open or short in the relay control or output wiring, connector problems, or a possible PCM fault. Start with the basic system checks, and if other codes are present, understand those first so you do not chase a symptom from another fault.
Confirm the fault path
To begin the confirmation, turn the vehicle to the ON mode. The important diagnostic logic is simple: if the PGM-FI subrelay is being controlled on, but the PCM does not receive the power supply voltage input, the PCM treats that as abnormal and stores P1659. Keep verification separate from the circuit testing; first reproduce the condition, then move into the relay power and wiring checks in order.
Check the +B_DBW power feed
Next, disconnect the PGM-FI subrelay and inspect the +B_DBW circuit at the disconnected PGM-FI subrelay socket. There are two power feed checks in this part of the routine, both with IG Mode OFF, and both should show 12 V battery voltage. If either power feed check is abnormal, the problem is in that circuit, and the power supply inspection has to be used to locate the failure before moving on.
Check for opens in the relay control and output circuits
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 72P connector. With IG Mode OFF, check the FI_SUB_RLY_CL- circuit between the disconnected PGM-FI subrelay socket and PCM connector A. Normal is less than 1 Ω. Then check the FI_SUB_RLY_OUT circuit the same way. Normal there is also less than 1 Ω. If either check is abnormal, treat it as a circuit problem and stay with the wiring diagnosis.
Check the relay output circuit for a short to ground
If the open-circuit 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 test, disconnect the PGM-FI subrelay, PCM connector A, the applicable EVAP purge connectors for the market, the EVAP leak check module connector where used, and the A/F sensor Sensor 1 connector. Use the proper open-or-shorted wire inspection method for this short-to-ground check, then inspect the FI_SUB_RLY_OUT circuit at the disconnected PGM-FI subrelay socket with IG Mode OFF. Normal is more than 1 MΩ. If it is abnormal, the problem is in that circuit.
PCM conclusion and final verification
Only after the +B_DBW power checks, the open-wire checks, and the short-to-ground check all show normal results does this diagnostic path point to a PCM problem. Do not jump there early. Verify the repair and confirm the code stays gone after the affected circuit or control issue has been corrected.
Takeaway
The clean way through P1659 is to prove relay power first, then prove continuity on the control and output circuits, then prove the output is not shorted to ground. If all of that passes, the remaining diagnostic direction is the PCM. For more diagnostic training, visit stepdiagnostics.com.
Final check
P1659 is often approached as a power feed and relay control circuit diagnosis before considering the PCM.
For more guided automotive diagnostics, visit STEP Diagnostics.
