What this code means
P1658 may indicate that the ECM/PCM is detecting an unexpected relay power condition in the electronic throttle control related PGM-FI subrelay circuit.
What the vehicle may do
- The vehicle may turn on the warning light.
- The vehicle may have throttle-related driveability symptoms.
- The code may be stored even if the symptom is not obvious during the initial inspection.
Possible fault areas
- Possible relay control circuit fault.
- Possible shorted output circuit fault.
- Possible issue with connected loads on the relay output feed.
- Possible PCM fault area after circuit checks are normal.
Diagnostic path
Opening context
On this 2017 to 2025 Honda CR-V with the 1.5 turbo, P1658 is tied to the ECM/PCM electronic throttle control system relay logic. In plain terms, the PCM may be seeing power when the PGM-FI subrelay is supposed to be off. The vehicle may turn on the warning light, may have throttle-related driveability symptoms, or may simply store the code. Broadly, you’re looking at possible relay control circuit issues, a shorted output circuit, connected loads on that feed, or, after the circuit checks pass, a possible PCM fault area. Before getting deep into pinpoint testing, start with the basic system checks and follow a structured diagnostic approach.
Duplicate the fault
Start by turning the vehicle to the ON mode. Then run the HDS ETCS TAC test. If that test result is not OK, the failure is duplicated, so continue with the circuit isolation path instead of chasing an intermittent that has not been proven yet.
Check the FI_SUB_RLY_CL- side for a short to ground
The first circuit check is the FI_SUB_RLY_CL- shorted wire inspection. Before disconnecting the PCM connector, jump the SCS line with the HDS and wait more than 1 minute. Then disconnect PCM connector A, the 50 pin connector, and disconnect the PGM-FI subrelay. Perform the shorted circuit inspection for the FI_SUB_RLY_CL- line. With the circuit commanded OFF, the normal condition for the short-to-ground check is more than 1 MΩ. If that check is abnormal, the problem is in the circuit.
Check the FI_SUB_RLY_OUT side for a short to power
Next move to the FI_SUB_RLY_OUT shorted wire inspection. Disconnect the PGM-FI subrelay, then before disconnecting the PCM connector, make sure the SCS line has been jumped with the HDS and wait more than 1 minute. Disconnect PCM connector A, the 50 pin connector. Then isolate the other loads on that output by disconnecting the fan control relay, the radiator fan relay, the EVAP canister purge valve connector, the A/F sensor Sensor 1 connector, and on USA and Canada models, the EVAP leak check module connector. Now perform the FI_SUB_RLY_OUT short-to-power inspection. With the circuit ON, the normal condition is not shorted. If this inspection is abnormal, the problem is in that circuit.
If the circuits test normal
If the FI_SUB_RLY_CL- check and the FI_SUB_RLY_OUT check both indicate normal conditions, the diagnostic path leaves the PCM as the remaining cause, and the result is a problem with the PCM. Do not jump to that conclusion before the relay control and output circuits have been isolated and checked in order.
Verification and takeaway
Keep verification separate from the circuit testing. After the fault area is handled, verify the repair and confirm the code stays gone. The takeaway on P1658 is simple: prove the ETCS TAC fault first, isolate the relay control side, isolate the relay output side and its connected loads, and only then consider the PCM as the remaining fault area. For more diagnostic training, visit stepdiagnostics.com.
Final check
P1658 often comes down to proving whether the relay control or relay output circuit is being held in the wrong state before considering the PCM as the remaining fault area.
For more guided automotive diagnostics, visit STEP Diagnostics.
