What this code means
P2135 may indicate that the PCM is seeing the two throttle position sensor signals disagree with each other.
What the vehicle may do
- The vehicle may have reduced throttle response.
- Warning lights may be present.
- Driveability complaints can occur when the throttle signals do not correlate.
Possible fault areas
- A possible fault area can be the throttle body internal throttle position sensor circuit.
- A possible fault area can be the THL1 and THL2 wiring.
- The PCM may be considered only after the other inspection areas test normal.
Diagnostic path
Opening context
On this 2016 through 2024 Honda Civic with the 2.0L non-turbo engine, P2135 means the PCM has seen the two throttle position signals disagree with each other. In plain language, TP sensor A and TP sensor B are not correlating the way the PCM expects. The vehicle may have reduced throttle response, warning lights, or driveability complaints, and the possible fault areas can include the throttle body internal sensor circuit, the THL1 and THL2 wiring, or, after the other checks pass, the PCM. Start with the basic system checks first, and if other codes are present, understand what they mean before chasing this one.
Confirm the fault with the scan tool
Begin the confirmation procedure by turning the vehicle to the ON mode. Then run the HDS ETCS(TAC) TEST. The scan tool path is PGM-FI, then Function Test, then ETCS(TAC) TEST. This code sets when the PCM sees a voltage deviation between TP sensor A and TP sensor B, so this first step is about confirming the electronic throttle control fault before moving into circuit testing.
Check THL1 and THL2 for a short between wires
Next is the THL1 and THL2 shorted-wire inspection. Before disconnecting the PCM connector, jump the SCS line with the HDS and wait more than 1 minute. Then disconnect the throttle body 6P connector and disconnect PCM connector E, the 80P connector. With PCM connector E disconnected, use the female terminals in IG Mode and perform the table-based inspection. In the OFF condition, the normal result for the THL1 and THL2 wire-to-wire short check is more than 1 MΩ. If this inspection is abnormal, treat it as a circuit problem. The table terminal callouts have to be clear before probing; if the exact test points are not available or cannot be confirmed, stop and verify the test points instead of guessing.
Check the throttle position sensor circuit
After the external circuit is normal, move to the TP sensor circuit inspection. Again, before disconnecting the PCM connector, jump the SCS line with the HDS and wait more than 1 minute. Disconnect PCM connector E, the 80P connector, and perform the inspection using the table for disconnected PCM connector E, female terminals, in IG Mode. For the throttle body internal circuit inspection in the OFF condition, the normal result is no continuity. This inspection can include the related inspection items, but if it fails, continue with the individual checks needed to identify which item failed. If this TP sensor circuit inspection is abnormal, the fault is in the throttle body. As with the previous table, do not probe unless the terminal locations are positively identified.
PCM conclusion
Only after the other inspection items show normal results should the PCM be considered the remaining cause. At that point, the diagnostic conclusion is that there is a problem with the PCM. Do not jump to that conclusion until the THL1 and THL2 wiring check and the throttle body internal circuit check have both been worked through correctly.
Takeaway
The key on P2135 is to keep the diagnosis in order: confirm the throttle correlation fault, check for a THL1 and THL2 wiring short, check the throttle body internal TP sensor circuit, and only then consider the PCM if everything else tests normal. For more diagnostic training, visit stepdiagnostics.com.
Final check
P2135 is best approached as a throttle position signal correlation diagnosis, not as a parts call.
For more guided automotive diagnostics, visit STEP Diagnostics.
