Toyota P0488 – throttle control fault on Land Cruiser 120

Toyota P0488 means “Exhaust Gas Recirculation Throttle Position Control Range/Performance.” On this Land Cruiser 120 with the 1KD-FTV engine, the fault was caused by an intermittent open circuit in the throttle-control wiring.

Toyota P0488 occurred intermittently on this Land Cruiser 120, also known internationally as the Land Cruiser Prado 120 (J120), with the 1KD-FTV engine. The vehicle could operate normally and then suddenly enter limp mode.

What does Toyota P0488 mean?

P0488 is labelled Exhaust Gas Recirculation Throttle Position Control Range/Performance. In this repair, that made the throttle body, throttle control motor and associated T2 circuit the relevant areas to inspect.

This article documents one specific cause: an intermittent open circuit in the L-B wire immediately behind connector T2. It does not establish that every Toyota with P0488 has the same fault.

Symptom

Techstream displayed P0488 – Exhaust Gas Recirculation Throttle Position Control Range/Performance.

Techstream display showing fault code P0488 Exhaust Gas Recirculation Throttle Position Control Range/Performance — Techstream recorded P0488 while the intermittent fault was present.

Initial inspection

I began by inspecting the throttle body and butterfly valve. There was no obvious mechanical fault, and the valve moved normally during the inspection.

Removed throttle body with the butterfly valve being checked for a mechanical fault — I inspected the throttle body and butterfly valve without finding an obvious mechanical fault.

I then located the throttle control motor and the connectors behind the engine so that I could trace the wiring harness further.

Throttle control motor and associated connectors behind the engine on a Toyota Land Cruiser 120 — The throttle control motor and connectors behind the engine.

Initial finding

Behind the engine, I found several wires with genuine damage. Copper was visible on some of them, and these faults needed to be repaired regardless of the P0488 code.

Several damaged wires with exposed copper in the wiring harness behind the engine — Several wires behind the engine had genuine damage and exposed copper.

The wires were spliced and insulated. The vehicle then operated normally, and I initially assumed that the problem had been solved.

Wiring harness behind the engine with several repaired and insulated wire splices — The damaged wires were repaired and insulated before the wiring harness was reassembled.

Pre-tinned conductor ends while soldering a wire repair in the wiring harness — One of the wiring repairs during soldering.

P0488 returned

P0488 returned after approximately two days. The initial wiring damage had been real and important to repair, but it was not the cause of this fault code.

Inspecting the T2 circuit

I therefore continued with the documented throttle control motor circuit. KTN-EL-002 Rev A shows all documented T2 circuits and highlights the fault path relevant to this repair:

Engine ECU Connector D pin 14 → L-B → T2 pin 6

KTN-EL-002 Rev A page 1 showing the T2 circuits and the open circuit marked between ECU D14 and T2 pin 6 — KTN-EL-002 Rev A, page 1: the T2 circuits and the P0488 fault path. Select the diagram to view it at full size.

KTN-EL-002 Rev A page 2 showing Engine ECU Connector D and the verified T2 cavity layout, 1 2 3 above 4 5 6 — KTN-EL-002 Rev A, page 2: Engine ECU Connector D and the verified T2 cavity layout. The viewing direction for T2 is not stated.

The T2 layout is documented with 1–2–3 in the upper row and 4–5–6 in the lower row. The diagram also shows that T2 pin 2 and pin 5 each connect to ground through a black wire (B). This does not mean that they necessarily share the same physical ground point.

Engine ECU Connector D under the dashboard on the passenger side of a Toyota Land Cruiser 120 — Engine ECU Connector D was the test point for terminal D14.

The actual fault

The actual cause was a broken L-B wire immediately behind connector T2. A break of this kind can make contact in one position and become an open circuit when the wire moves or vibrates. This explains why the fault could be intermittent and why the vehicle operated normally between events.

Repair

The L-B wire was repaired, insulated and returned to the harness so that the connection between ECU D14 and T2 pin 6 was restored. The photograph of connector T2 below was taken after the repair; the broken wire itself is not visible in the image.

Result

After the L-B wire at connector T2 had been repaired, continuity was restored in the documented P0488 fault path. The fault has not returned since the repair.

Summary

Fault: P0488

Circuit: ECU D14 → L-B → T2-6

Cause: Intermittent broken wire immediately behind connector T2

Repair: Wire repaired