U0673

Code

Generic U — Network/User

Lost Communication With Ion Sense Module

Brand: Generic

Type: U — Network/User

Views: UK: 23 EN: 26 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open, short or intermittent wiring between ECU and Ion Sense Module
Corroded or damaged connector pins at module or ECU
No power or poor ground at the Ion Sense Module
Faulty Ion Sense Module
Fault or interference on the vehicle data bus (CAN, LIN, etc.)
Blown fuse or fusible link supplying the module

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Loss of ion-sensing functions (e.g., misfire/knock detection, combustion monitoring)
Stored related DTCs in other modules
Possible rough idle, misfire detection errors or reduced performance (depending on vehicle fallback)
Inability to run certain diagnostics or OBD readiness monitors

What to check

Read all stored and pending DTCs and freeze frame data from all modules; note related network codes
Inspect Ion Sense Module connector and wiring for corrosion, bent pins, contamination and secure locking
Check fuse(s) and fusible links for the module circuit
Measure module supply voltage and ground with key ON (expected ~battery voltage and near 0V ground)
Verify data bus activity with a scan tool — confirm module appears on network or shows communication errors
Check CAN/LIN bus voltages and resistance between bus wires (end-to-end termination ≈ 60 ohms for CAN)

Signal parameters

Module supply voltage: ~11–14 V with engine running (key ON should show battery voltage)
Module ground: near 0 V; high resistance to chassis indicates poor ground
CAN bus idle voltages (typical, vehicle dependent): CAN H ≈ 2.5–3.5 V, CAN L ≈ 1.5–2.5 V, common-mode ≈ 2.5 V
CAN differential voltage when active: pulses up to ~2 V differential (protocol/baud dependent)
Nominal bus termination resistance: approx. 60 ohms (two 120 ohm terminators in parallel) across CAN H and CAN L
Communication baud: commonly 250 kbps or 500 kbps for CAN (vehicle specific)

Diagnostic algorithm

Verify and record DTC U0673 and any additional codes from all modules with a capable scan tool.
Review vehicle service information and TSBs for known Ion Sense Module or network issues and required procedures.
Visually inspect the Ion Sense Module connector and harness for physical damage, corrosion, and secure connection; repair as needed.
Check module power and ground circuits: verify fuse, measure battery voltage at module power pin with key ON, verify ground continuity to chassis.
Use a scan tool to list modules on the data bus and check if the Ion Sense Module is present/responding. Note time stamps and any communication errors.
Measure CAN/LIN bus voltages at the module connector and at the ECU; confirm proper idle voltages and termination resistance (~60 ohms).
If bus voltages are abnormal, isolate the short/open by disconnecting modules one at a time or using backprobe tests to locate the fault.
Perform a wiggle test of the harness and connectors while monitoring communication and DTC status to find intermittent faults.
If the wiring and bus check good, replace or bench-check the Ion Sense Module per manufacturer instructions. Reprogram/relearn if required.
Clear codes and perform functional test/road test to confirm repair. If issue persists, suspect ECU or network module fault and follow manufacturer diagnostic flow for controller replacement.

Likely causes

Damaged or corroded connector/wiring to Ion Sense Module
Loss of module power or ground
Faulty Ion Sense Module
Data bus fault (short to battery/ground or open)
ECU communication fault or software issue

Fault status

⚠️ Status

Lost communication detected between vehicle network controller and Ion Sense Module. Communication may be intermittent or permanent; further diagnostics required to identify wiring, power/ground, bus, module, or ECU cause.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours