OBD Guide
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U1842

Lost Communication With ECM/PCM

U1842 is an OBD-II diagnostic trouble code meaning: Lost Communication With ECM/PCM. Common causes: open or short circuit in the can bus, ecm/pcm power supply problems. Estimated repair cost: ~$278.

Severity
🔴 High
Can you drive?
Do not drive — repair immediately
Approx. repair cost
~$278 (est.)

Symptoms

  • Check Engine light is on
  • Unstable engine operation
  • Failure of some vehicle systems
  • Problems with diagnostics (not all blocks are available)
  • Gearbox malfunctions

Causes

  • Open or short circuit in the CAN bus
  • ECM/PCM power supply problems
  • Main control unit malfunction
  • Damage to connectors or corrosion of contacts
  • Grounding problems

How to Fix

  1. Check fuses for ECM/PCM
  2. Inspect the condition of the CAN bus wiring
  3. Check ECM/PCM connectors and contacts
  4. Check the power supply and grounding of the control unit
  5. Diagnose ECM/PCM on a bench

Related codes

U0100U0101U0140

FAQ

What does the U1842 code mean?

U1842 is an OBD-II diagnostic trouble code that indicates: Lost Communication With ECM/PCM

What causes a U1842 error code?

The most common causes of U1842 include: Open or short circuit in the CAN bus; ECM/PCM power supply problems; Main control unit malfunction; Damage to connectors or corrosion of contacts.

How do I fix a U1842 diagnostic trouble code?

To fix U1842: Check fuses for ECM/PCM. Inspect the condition of the CAN bus wiring. Check ECM/PCM connectors and contacts. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with U1842?

Do not drive — repair immediately

How much does it cost to fix U1842?

The estimated repair cost for U1842 is ~$278. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat