P2101 on a 2013-2017 Honda Accord: Start With Carbon on the Throttle Body

On a 2013-2017 Honda Accord with the 2.4L (K24W1) or 3.5L (J35Y1, J35Y2), P2101 means the throttle valve is not following the opening the PCM commands. Carbon on the throttle plate and bore is the most likely cause, with outdated PCM software next on 2013-2015 2.4L no-starts. Pull the intake duct and watch the valve during a scan tool throttle test. Diagnose it before relying on the car.

What does P2101 mean on a 2013-2017 Accord?

P2101 (Electronic Throttle Control System (ETCS) Malfunction) is a throttle position control error. The throttle body carries an electric actuator motor, the throttle valve, and two throttle position (TP) sensors, A and B. The PCM reads the accelerator pedal position (APP) sensor, works out a target opening, and drives the motor on the MTR1 and MTR2 lines to reach it, while TP sensor A reports where the valve actually sits. The PCM's throttle driver is powered through the ETCS control relay in the under-hood fuse/relay box.

The PCM compares target and actual opening continuously. A sticking or carbon-coated valve, a weak motor, a bad sensor signal, a wiring fault or a PCM fault can all open that gap.

The PCM sets P2101 when the actual opening misses the target by more than the limit for the commanded angle for 250 milliseconds or more with the valve moving toward closed, or 500 milliseconds or more moving toward open. On both engines:

• The monitor runs continuously, with battery voltage at 6.0 V or more and the ignition ON.
• At a 2 degree target, actual is off by 4 degrees or more.
• At 6 degrees, off by 5.4 degrees or more.
• At 10 degrees, off by 5.7 degrees or more.
• At 15 and 90 degrees, off by 6 degrees or more.
• None of the fix-first codes in the diagnosis section is active.

It is a one drive cycle code: the PCM turns the MIL on and stores a pending code, a confirmed code and freeze data at once. The light goes out if the fault does not return in three consecutive trips in which the check runs. The PCM also has a fail-safe function that controls the throttle valve to avoid danger when it sees a fault.

These codes share the same throttle body and circuits. All use 200 milliseconds or more unless noted:

• P2118: actuator current 11 A or more.
• P2135: TP sensors A and B disagree by 1.8 degrees or more at 0 degrees, or 14.7 degrees or more at 83.3 degrees.
• P2176: closed position learning not finished in time after switch-off, or the learned position out of range, for 2.0 seconds or more.
• P0122 and P0222: TP sensor A or B at 0.3 V or less.
• P0123 and P0223: TP sensor A or B at 4.8 V or more.
• P1659: no voltage from the ETCS control relay.

If P2195 (A/F sensor 1 signal stuck lean) is stored alongside P2101, sort out P2101 first.

What symptoms does P2101 cause on the Accord?

• Check engine light on.
• Cranks but will not start, the complaint Honda addressed on 2013-2015 2.4L cars.
• Starts for a moment, then dies.
• The code sets with no drivability complaint at all.

What causes P2101 on the Accord, most likely first?

Here is how I would line them up on this Accord.

How do you diagnose P2101 on a 2013-2017 Accord?

You will need a scan tool with ETCS test, PCM reset, SCS and reprogramming functions, basic hand tools, throttle plate cleaner, paper towels, a new throttle body gasket and a jumper battery for any software update. Record the freeze data first; the confirmation drive uses it.

Any of these codes, when active, stops the P2101 check from running, so fix them first:

• P0122, P0123, P0222, P0223 and P2135 on the TP sensor circuit
• P2118 and P2176 on the throttle actuator
• P1659 on the ETCS control relay (2015 models on)
• P2122, P2123, P2127, P2128 and P2138 on the accelerator pedal position sensor (2013 and 2014 models)

What if the obvious fix does not work?

Cleaning alone does not always hold. The code can come back, and that is when the software update (on a 2013-2015 2.4L) or a new throttle body comes into play. A couple of mistakes can also undo the job:

• Spraying cleaner straight into the throttle body, where it can reach the electronics.
• Reusing the old throttle body gasket.

If P2101 returns after the software update on a 2013-2015 2.4L, go back to the full diagnostic path, starting with the valve check. Your stop point is the PCM: when the throttle body and wiring check good and the software is current, substitute a known-good PCM and replace it only if the fault moves.

How do you confirm the repair?

The PCM idle learn is required after replacing, resetting or updating the PCM, and after cleaning or replacing the throttle body; clearing codes alone does not call for it. To confirm, reconnect everything, exit SCS mode, switch to ON, reset the PCM and do the idle learn:

• Turn off all electrical loads, reset the PCM, switch to ON and wait 2 seconds.
• Start the engine and hold 3,000 rpm with no load (P or N, manual in neutral) until the radiator fan comes on or coolant reaches 194°F (90°C).
• Idle about 5 minutes with the throttle fully closed, not counting radiator fan running time.
• Switch OFF, jump the SCS line with the scan tool, wait 60 seconds and exit SCS mode.

To disconnect the battery within an hour of switching off after the idle learn, jump the SCS line and wait 60 seconds first, or the PCM may lose what it learned.

Then test-drive for several minutes within the freeze data conditions and check for a pending or confirmed P2101. No P2101 means the repair is complete; if you substituted a known-good PCM for the test, refit the original afterward, then move on to any other stored code. If P2101 returns, check the connections and terminals at the throttle body and PCM, clean the throttle body and start again by duplicating the fault. If the PCM was updated, substitute a known-good PCM and recheck.