EN

Severity: High Code type: Generic (all makes)

P2100 Code: Throttle Actuator Control Motor Circuit/Open

The computer can't push current through the throttle motor – the circuit to the throttle body looks broken.

At a glance

Severity: 4/5 – High4/5

Severity: High

Meaning
Throttle Actuator Control Motor Circuit/Open
System
Speed & Idle Control · Powertrain
Safe to drive?
With caution
Typical repair cost
$20–$1,600
DIY difficulty
Moderate

On a drive-by-wire engine the throttle plate is turned by a small DC motor inside the throttle body, fed by two wires from an H-bridge driver in the engine computer (PCM). The PCM watches the current it sends; when it commands the motor but almost no current flows, it concludes the circuit is open and sets P2100. It then switches the motor off and lets the return springs park the plate at a slightly open limp-home position, which is why the engine keeps running at a fixed fast idle. Most cases are a loose or corroded throttle body connector or a broken wire in the harness; a burned-out motor inside the throttle body comes next. On some makes the circuit also runs through a fuse or a throttle motor relay, which can fail as well.

How to read P2100

How to read P2100P12213004
  1. P Powertrain
  2. 2 Generic (SAE)
  3. 1 Fuel & air metering
  4. 00 Specific fault

Symptoms

  • Engine runs at a steady fast idle and ignores most of the gas pedal
  • Very little power – the car only creeps or crawls up hills
  • Electronic throttle or wrench warning light alongside the check engine light
  • Cruise control does not work
  • Automatic transmission may shift early or feel harsh because of the fixed throttle
  • Problem sometimes appears after the throttle body was cleaned or unplugged

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Throttle body connector unplugged, not fully latched, corroded or with spread motor terminals 30%
  2. Broken or chafed motor wire in the harness between PCM and throttle body 22%
  3. Open motor winding or worn brushes inside the throttle body 20%
  4. Blown throttle control fuse or failed throttle motor relay (on makes that use one) 14%
  5. Failed motor driver stage inside the PCM 8%
  6. Water or oil wicked into the connector, creating an intermittent open 6%

Diagnosis step by step

Diagnostic flow: P21001Record all codes before clearing2Inspect the throttle body connector3Measure the motor winding4Check the two motor wires end to end5Check fuse and relay where fitted6Clear and verify with live data

  1. Record all codes before clearing

    Note P2100 together with any throttle position or motor current codes such as P2118 or P2119, and the freeze frame. P2100 alone points at the motor power path; several sensor codes at once point at the whole connector or a shared harness section.

    Tools: OBD-II scanner

  2. Inspect the throttle body connector

    Ignition off, unlatch the connector and look for green corrosion, pushed-back pins or terminals that grip loosely. The two motor pins carry the most current and are the ones that burn or loosen first. Reseat it until the lock clicks.

    Tools: Flashlight, Screwdriver

  3. Measure the motor winding

    With the connector off, measure resistance across the two motor pins on the throttle body side. Many units read only a few ohms (roughly 1–5 Ω, check the spec for your engine); an infinite reading means the motor itself is open and the throttle body has to be replaced.

    Tools: Multimeter

  4. Check the two motor wires end to end

    Back-probe or use the PCM pin-out to test each motor wire from PCM to throttle body; each should read well under 1 Ω. Flex the harness where it crosses the valve cover or bends near the engine mount while watching the meter, because breaks there often only open when the engine rocks.

    Tools: Multimeter

  5. Check fuse and relay where fitted

    Some vehicles feed the throttle motor through a dedicated fuse or relay in the underhood box. Check the fuse on both test points and confirm battery voltage at the relay output with the key on; a relay that clicks but passes no voltage is faulty.

    Tools: Multimeter, OBD-II scanner

  6. Clear and verify with live data

    Clear codes, cycle the key and watch commanded throttle (PID 4C on generic scanners) against actual throttle position at idle and during a light rev. They should track closely; if P2100 returns with a good motor and wiring, the PCM driver is suspect.

    Tools: OBD-II scanner

Where the parts are

Ignition: coils and spark plugs per cylinder – P21001234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Clean and re-pin throttle body connector No $80–$250
Repair broken motor wire in harness No $120–$400
Replace throttle control fuse or relay Yes $20–$120
Replace electronic throttle body and relearn No $350–$900
Replace and program PCM (driver fault) No $700–$1,600

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Notes by brand

Nissan

Nissan uses P2100 for its throttle control motor relay circuit, a relay housed in the underhood power distribution module (IPDM E/R). Check the relay feed and its fuse before condemning the throttle body.

Emissions / smog test impact

Will fail

P2100 turns on the check engine light, so an OBD-based smog or emissions inspection fails. The car is also hard to drive to the station in limp mode – repair it first and let the monitors complete.

Frequently asked questions

Why does my engine sit at about 1,300 rpm and ignore the pedal?

When the PCM cuts power to the throttle motor, springs in the throttle body hold the plate slightly open. That fixed opening gives a fast idle and a little power to limp, but the pedal can no longer open the throttle further.

Will cleaning the throttle body fix P2100?

Rarely. P2100 is an electrical fault in the motor circuit, not a sticking plate. Cleaning only helps if the connector was left loose afterward – which, ironically, is a common way to cause the code.

How is P2100 different from P2102 and P2103?

P2100 means the PCM sees an open circuit – no current flowing at all. P2102 and P2103 mean current is flowing but is too low or too high, which points more toward high resistance, shorts or a binding motor.

Can I just replace the throttle body?

Only after the resistance check. If the motor winding measures correctly on the bench, a new throttle body won't help, and the fault is in the connector, the harness or the supply feeding the motor.

Sources