Renault: Mot 1654

Posted on: April 20, 2026 Category: Classic Car Maintenance

If you’ve landed here searching for “MOT 1654 Renault” , chances are you either own a Renault with the personalized or vintage registration plate MOT 1654, or you’re trying to decode an old logbook.

First, let’s clarify: MOT 1654 is not a Renault model number (like the Renault 4 or 5). It is almost certainly a vehicle registration mark. Given the format (three letters followed by three numbers), this points to a UK registration issued between late 1963 and early 1965.

If you are the proud owner of a Renault from that era—such as a Renault 4 (R4) , Renault 8, Renault Caravelle, or Renault Dauphine—then MOT 1654 is a fantastic piece of history. But here is what you need to know about getting it through the actual MOT test.

On the hugely popular 1.5 dCi engine (found in the Renault Megane III, Clio IV, Captur, and Nissan Qashqai), code 1654 relates to the EGR valve. The EGR valve recirculates exhaust gases back into the intake to reduce NOx emissions. The ECU runs regular "learning" cycles to calibrate the EGR valve position. If the valve sticks or the potentiometer reads out of range, code 1654 appears.

Symptoms on diesel:

A: It is likely an intermittent open circuit (loose connector or chafed wire that occasionally touches ground). The ECU stores the code as a history fault. It will become a permanent fault soon.

In Renault’s proprietary diagnostic language, DTC 1654 corresponds to: "Injector control circuit – Cylinder 4 – Open circuit or short circuit to ground/battery."

Alternatively, on some diesel Renault models (specifically the 1.5 dCi K9K engine), code 1654 can refer to: "EGR Valve (Exhaust Gas Recirculation) learning limit – Position feedback inconsistency."

To accurately resolve MOT 1654 Renault, you must first know which engine you have. The code behaves differently on petrol vs. diesel systems.

Vehicle: 2004 Renault Laguna II 1.9 dCi (F9Q-804)
Mileage: 142,000 miles
Fault: Intermittent loss of power, engine light, code MOT 1654. mot 1654 renault

What the first garage did: Replaced the turbocharger ($1,100) – Code returned after 80 miles.

What fixed it: A second mechanic found a cracked vacuum hose near the brake servo. The tiny leak (3mm split) was causing the turbo actuator to see only 0.3 bar instead of 0.8 bar. The ECU, seeing sluggish vane movement, logged overboost when the system finally caught up.

Cost of final repair: $3 (silicone hose) + $80 diagnostic. Lesson: Always start with vacuum lines.

After cross-referencing Renault’s technical bulletins and owner forums, MOT 1654 typically refers to a Turbocharger Pressure Regulation Fault — more precisely, a deviation between the requested boost pressure and the actual measured boost pressure (often a positive deviation or overboost).

In plain English: The engine’s ECU (Engine Control Unit) commands a certain amount of boost from the turbocharger, but the sensors report that the system is producing too much pressure for too long. Posted on: April 20, 2026 Category: Classic Car

Equivalent OBD-II codes (generic): P0234 (Turbocharger Overboost Condition) or sometimes P0299 (Underboost — though that’s less common for 1654).

This fault is rarely caused by a single "magic bullet" component. It is usually a symptom of one of the following underlying issues:

To clear code DF1654, you must address the root cause, not just erase the code. Here is the recommended workflow:

1. Check the Physical Components First

2. Inspect the Wiring

3. Live Data Analysis

4. Test the Accelerator Pedal