U3024

What it means

U3024 means a control module has compared two of its ignition-related power inputs, the ignition on/run feed and the start feed, and found that they do not agree. For example, one input showed the ignition as on while the other showed it as off or in the wrong state for the key position. Which module sets the code and which wire is 'Circuit B' depends on the vehicle, so use the model-specific wiring diagram.

Symptoms

• Warning lights on the dash, sometimes with several lit at once
• Engine slow to start, fails to start, or cranks without firing
• Intermittent stalling or loss of power with the ignition on
• Accessories or modules dropping out or behaving erratically when the key is turned
• Other communication or low-voltage fault codes stored alongside U3024

Possible causes

• Weak or poorly connected battery, or loose or corroded battery terminals, causing voltage dips during start-uplikely
• High resistance, corrosion or damaged pins in the ignition feed wiring or connectors to the affected modulelikely
• Worn or faulty ignition switch, start button or related switch contacts giving inconsistent on/start signalspossible
• Blown fuse, faulty relay or poor earth in the ignition or start circuit supplying the modulepossible
• Poorly fitted aftermarket alarm, remote start or tracker wiring interfering with the ignition circuitspossible
• Internal fault in the control module's power input stage, or an outdated module calibration where the manufacturer lists one as a known causerare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including battery voltage and ignition state when the code set
2. Test the battery state of charge and the charging system, and check the terminals and main earth connections for tightness and corrosion
3. Check the relevant fuses and relays and inspect their sockets for heat damage or poor contact
4. Inspect the wiring and connectors at the affected module and the ignition switch for chafing, moisture, corrosion or spread pins, and look for any aftermarket wiring spliced in
5. Using the model-specific wiring diagram, measure the ignition on and start feeds at the module with the key in each position and compare them
6. Carry out voltage drop tests on the ignition feed and earth circuits while operating the switch and while cranking
7. Wiggle-test the harness and switch with a meter or live data connected to find intermittent faults
8. Check for manufacturer service information on this code for the model, and only if the module is suspected after the wiring is proven good, confirm its supply and earth before replacing it

How to fix

• Charge or replace a weak battery and clean and tighten the terminals and earth points
• Repair or replace damaged wiring, terminals or connectors in the ignition feed circuit
• Replace a faulty ignition switch, start switch or relay as confirmed by testing
• Replace blown fuses only after finding and correcting the cause of the overload
• Remove or correctly rewire faulty aftermarket accessories connected to the ignition circuits
• Replace or reprogram the control module only when testing confirms it is faulty or the manufacturer lists an update as the cure, then clear the code and road test

Can I keep driving?

Nearby codes

• U3023GenericControl Module Input Power Circuit A - Ignition Input On/Start Circuit Correlation
• U3025GenericControl Module A Disable Circuit/Open