U3027 code meaning
Control Module A Disable Circuit High
What U3027 means
U3027 is the high-side counterpart: the disable line to module A reads above its valid range, as with a short to battery voltage or a neighbouring wire. In an active-low design such as the one in Siemens patent US7596436B2, where pulling the shutdown path to ground blocks the output stages, a line stuck high means module A keeps its enable and can no longer be switched off over the hard-wired path. That removes the independent safety layer FCA's patent US10676100B2 is built around, where losing a shutoff line could let a hybrid keep producing torque. Systems therefore treat this case strictly and usually disable the function by other means. No manufacturer documents U3027 publicly; check for a short to a powered wire in the harness and for water in connectors.
U3027 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3027
- Function locked out by the safety concept, system warning shown
- Vehicle may not become ready to drive
Common causes of U3027
- Most likelyDisable wire shorted to a battery or supply wire
- PossibleMoisture or corrosion bridging pins in a connector
- Less likelyOutput driver of the supervising module stuck high
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Module disable aControl wiring
What each part of U3027 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 27 | The exact fault in that area. |
What to do next
- Note U3027 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3027
What does U3027 mean?
U3027 means "Control Module A Disable Circuit High". U3027 is the high-side counterpart: the disable line to module A reads above its valid range, as with a short to battery voltage or a neighbouring wire. It is a generic code, so it means the same on every make.
Is it safe to drive with U3027?
Drive gently and only to a workshop. With U3027 the car can go into limp mode (reduced power) to protect itself.
Will U3027 fail an emissions test?
U3027 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3027 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will U3027 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.