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P2118 Diagnostic and Fix for 2005 Toyota Highlander with Throttle Response Issues

Model: '05 Highlander Fault Code: P2118 Posted: 2019-12-27 07:51

My 2005 Toyota Highlander with a 4-cylinder engine will not run properly. The engine turns over and starts, but immediately dies after startup. I checked the fuses and found a blown 10-amp ECU-IG fuse under the dashboard. After replacing it, the car still fails to start consistently. Using an OBD2 scanner, I retrieved only one fault code: P2118 — Throttle Actuator Control Motor Current Range/Performance. P2118 is triggered by the Powertrain Control Module (PCM) when the throttle actuator control motor is out of its expected operating range or not performing correctly. I replaced the entire throttle body assembly, including the motor unit. The car now starts and runs, but exhibits very poor throttle response — only reaching 1500–2000 RPM when accelerating to the floor. Idle speed is also elevated (around 1000 RPM) with noticeable fluctuations. I disconnected the throttle body wiring harness, but the car still starts and idles normally under these conditions. After replacing the throttle body a second time, I observed identical symptoms. Given this lack of throttle response, am I experiencing a fail-safe or limp mode? Is it possible that the PCM needs to be replaced? Additional diagnostics show that when the engine is running, there are intermittent voltage spikes (up to 18 volts) on Pin #3 (E2) at idle — which disappear when the gas pedal is pressed. These blips are only visible with a digital voltmeter and not detected by an analog meter. I have verified that both the ECU-IG and ECU-B fuses measure 13.8 volts across, indicating power supply is present in the fuse box. However, no voltage is detected at Pin 6B (+BM) on the PCM connector, which should provide power to the throttle motor. I have confirmed that the correct fuse (ETCS, 10A) was missing entirely — it was not installed in the fuse block. After installing this fuse, the car started and ran normally without any further issues. This suggests a critical failure in the electrical path from the ETCS fuse to the PCM's throttle control circuit. The absence of voltage at Pin 6B explains why P2118 is set and why throttle response is absent — the system cannot communicate with or power the throttle actuator motor. Conclusion: The issue was not a faulty throttle body or PCM, but rather an open circuit due to a missing ETCS fuse. Replacing the correct 10A ETCS fuse resolved the problem completely.

Related fault codes

P2118

Comments (13)

Anonymous 2019-12-27 11:06

Check wiring diagrams for the ETCS circuit — resources like bbbind.com can provide detailed schematics. Verify voltage from the ETCS fuse to the PCM and ensure proper power delivery to the throttle control motor. Please share your findings.

Anonymous 2019-12-28 18:08

Currently working on this issue; will update with further insights as they become available.

Anonymous 2019-12-30 21:23

Voltage readings from the ETCS fuse (to PCM) with engine running: 13.8 volts. With the engine warm, I disconnected the throttle body harness to measure voltages at the PCM: - White / Pin 1 (M-) → 0.16 V - Black / Pin 2 (M+) → 0.16 V - Brown / Pin 3 (E2) → 0 V (with blips up to 18V every few seconds at idle; spikes disappear when gas pedal is pressed) - Black/Red / Pin 4 (VTA2) → 4.15 V - Yellow / Pin 5 (VC) → 4.98 V - Black/White / Pin 6 (VTA1) → 4.14 V Note: The digital voltmeter shows intermittent spikes on Pin #3 during idle, which vanish when the pedal is pressed. Analog meter reads zero — this suggests a transient signal or grounding issue. Does this data help clarify the problem?

Anonymous 2019-12-30 22:44

Confirm that the ECM input side of the ETCS fuse has battery voltage. This power supply enables the throttle actuator control circuit in the PCM. I don’t have access to an official wiring diagram, but I can help guide you through identifying the correct connector.

Anonymous 2019-12-31 09:39

Yes — if I understand correctly, are you asking whether there is battery voltage at the input side of the ECM? I initially thought the output side of the ETCS fuse was relevant. I’ll now check which PCM connector to test, turn on ignition, and measure voltage from the fuse to the ECM input terminal.

Anonymous 2019-12-31 10:39

Confirmed: Pin 6B (+BM) in the ECM connector provides power for the throttle actuator motor. To verify this circuit: - First, back-probe the connector. - If voltage is present there, then disconnect and test the front of the connector. Without proper voltage at this point, the PCM will set P2118 and enter limp mode. Thanks for sharing the schematic — it’s very helpful.

Anonymous 2020-01-01 13:26

Happy New Year! To clarify: I previously measured voltages at the ETCS fuse but was unsure which one to test. I found both an ECU-IG and ECU-B fuse in my vehicle — both showed 13.8 volts across. I reviewed the attached photos of the fuse box layout and confirmed that Pin 6B on connector B is the correct location for the +BM power feed. After confirming pin numbering via wire color positioning, I measured voltage at both sides of the connector — zero volts detected in both back-probe and front-side measurements. This indicates no power reaching the ECM input. Based on the wiring diagram, there should be a direct path from the fuse to Pin 6B. No intermediate components are visible in that section. Any suggestions for possible failures or missing connections?

Anonymous 2020-01-01 14:20

In the fuse block diagram — did you check voltage at the 10A ETCS fuse? This is the critical component powering the throttle actuator circuit.

Anonymous 2020-01-01 14:27

I now see the correct fuse you're referring to! I will measure it later today and post results this evening.

Anonymous 2020-01-01 21:19

Voltage at the proper ETCS (10A) fuse reads 13.9 volts — confirming power is present in the fuse itself.

Anonymous 2020-01-02 08:57

Verify that voltage is stable and present near or outside the fuse block. Use a piercing wire to test continuity if needed. If no voltage, the issue lies between the fuse and the ECM input.

Anonymous 2020-01-03 16:09

The car is now running perfectly! While inspecting the fuse box during wiring checks, I realized I had misidentified the ETCS fuse location — it was completely missing! After installing the correct 10A ETCS fuse, the vehicle started and ran normally. Thank you so much for your detailed guidance — this resolved a critical issue that could have cost me hundreds in repairs.

Anonymous 2020-11-01 15:46

Hi — I own a 2012 Toyota Corolla. Today, my battery dropped unexpectedly. I used a spare battery and accidentally touched the positive and negative terminals with an iron rod, causing a short. After reconnecting, the car started but had no power to the engine — check engine light illuminated. Using OBD-II Bluetooth, I retrieved code P2118. After clearing the fault and restarting, the error persisted. I checked the under-hood fuse box and replaced the 10A red-colored fuse (likely the ETCS fuse). After restart, the car ran normally — no more errors. This resolved the issue without needing a new PCM or throttle body. Thanks for helping me avoid unnecessary repairs!