Home›Trouble Codes›P0487

P0487 — Egr Throttle Control Circuit Open

Generic OBD-II · all makesPowertrain (engine & transmission)

P0487 indicates the Powertrain Control Module has detected an open electrical circuit in the EGR throttle control system. This means the circuit supplying current to the EGR throttle actuator motor has a break—either in the wiring between the PCM and valve or internally within the actuator itself—preventing the valve from being commanded to move.

Symptoms

What causes it — most likely first

1. Failed EGR throttle valve actuator

The internal electric motor windings have opened due to wear or heat damage, creating infinite resistance so no current flows. This is the most common cause.

2. Open circuit in wiring harness

A break, chafing, or severed wire in the control circuit or power/ground feed between the PCM and the EGR throttle valve interrupts electrical continuity.

3. Corroded or loose electrical connector

Moisture intrusion, pin corrosion, or a backed-out terminal at the EGR throttle valve connector creates a high-resistance open circuit.

4. Rodent or aftermarket damage

Chewed wiring insulation or improper prior repair splices can create an open in the low-current control circuit.

5. PCM output driver failure

Rarely, the internal transistor that grounds the control circuit inside the PCM may fail open, preventing circuit completion. This should only be considered after wiring and actuator are verified good.

How it's diagnosed

  1. Visually inspect the EGR throttle valve electrical connector and wiring for damage, corrosion, or disconnection
  2. Measure resistance across the EGR throttle actuator motor terminals; infinite or out-of-spec resistance indicates an internal open requiring valve replacement
  3. Check continuity of the control circuit wiring between the PCM connector and the EGR throttle valve connector to locate any breaks
  4. Command the EGR throttle valve on with a scan tool while monitoring circuit voltage; absence of voltage drop with command active indicates an open upstream
  5. Verify PCM power and ground supplies are stable; if all external circuits and the actuator test good, evaluate the PCM output driver (rare)

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0480 — Fan 1 Control CircuitP0481 — Fan 2 Control CircuitP0482 — Fan 3 Control CircuitP0483 — Fan Rationality CheckP0484 — Fan Circuit Current HighP0485 — Fan Powerground Circuit

Frequently asked

Can I drive safely with a P0487 code?

Short trips are possible, but prolonged driving is not recommended. A disabled EGR system increases combustion temperatures, which can cause engine knock and potential damage over time, and will likely cause emissions test failure.

Is the EGR throttle valve the same as the main EGR valve?

No. The EGR throttle valve is a separate plate (often in the intake or EGR cooler path) that regulates airflow to control EGR rates, distinct from the primary EGR valve that meters exhaust gas, though they function together.

My mechanic wants to replace the PCM; is that necessary?

No. PCM failure causing this specific open-circuit code is uncommon. The problem almost always lies in the actuator itself or the wiring/connectors between the valve and PCM. Only consider the PCM after confirming the component and harness are definitively good.

What exactly does 'Circuit Open' mean?

It means the PCM detects infinite electrical resistance or a complete break in the circuit, so electrical current cannot flow to the EGR throttle motor. This is typically caused by a broken wire, bad connector, or failed internal motor windings.