U0151

What does U0151 mean?

U0151 is a Network (CAN bus, module communications) fault code. It indicates: Lost Communication with Restraints Control (RCM) Module.

This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.

Symptoms commonly associated with this code

Symptoms that drivers often report alongside this code. Not all may apply to every case:

• • Airbag warning light stuck on, and it usually won't go out on its own
• • SRS or 'Service Airbag' message on the dash, depending on the make
• • A warning chime when you switch the ignition on
• • On some cars, the seatbelt warning behaves oddly or stays lit
• • Engine runs and drives completely normally, nothing changes in how the car pulls
• • Occasionally other warning lights join in if the same CAN fault is knocking out more than one module

Possible causes

Causes commonly associated with U0151, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.

1. 1. Corroded or damaged wiring at the airbag module connector, by far the usual culprit, especially where damp has got into the centre console or under a seat
2. 2. Connector pins backed out, bent, or green with corrosion, which kills the CAN signal even if the wires themselves look fine
3. 3. Blown fuse feeding the module, often a 10A in the body control fusebox, so always worth a two-minute check before anything else
4. 4. Poor earth at the module mounting point or harness ground, which causes intermittent dropouts that come and go with road vibration
5. 5. The module itself failed internally, frequently from water ingress, common on cars where the airbag module sits low in the centre tunnel and a leak has tracked down to it
6. 6. A wider CAN bus fault elsewhere on the network dragging the airbag module offline along with other modules
7. 7. Software mismatch after a recent module swap or reflash where the coding wasn't completed properly

How mechanics typically diagnose

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.

1. 1. Scan every module, not just the airbag one. If U0151 is sitting next to a pile of other U-codes like U0100 and U0140, the problem is the CAN network itself, not the airbag module. A lone U0151 points at the module's own wiring or supply
2. 2. Check the airbag module fuse and confirm you've got around 12V at the supply pin with the ignition on, plus a good earth. Low or no voltage here explains the whole thing
3. 3. Get under the carpet and into the connector. Look for water staining, green corrosion on the pins, and any connector that isn't fully clicked home. This is where most of these jobs are won
4. 4. Wiggle-test the harness and connector with the scan tool watching live, because a lot of these faults are intermittent and only show up when the car's moving
5. 5. Run a CAN communication test with a proper scan tool to see if the module answers a direct query. If it never responds and the supply and earth are good, the module is the suspect
6. 6. Only once power, earth and wiring all check out should you condemn the module. Replacement means VIN-specific programming, so don't buy a unit until you're certain

Common questions about U0151