What are common causes for U0023?

CAN-H/CAN-L shorted together (high) · Gateway module routing CAN messages incorrectly (low) · CAN terminating resistor (120 Ω) drifted out of spec (low)

What symptoms does U0023 show?

Multiple warning lights may illuminate · Affected modules may go into limp mode or shut down · Specific functions inoperative depending on module · Diagnostic tools may show communication faults

Network generic / SAE

U0023

Low Speed CAN Communication Bus (+) Shorted to Bus (-)

CAN-High and CAN-Low on the low-speed comfort bus are shorted together. Both differential and single-wire modes fail; comfort modules drop offline.

SystemNetwork

Typegeneric / SAE

GroupU0

Range / number– / 23

Possible causes

CAN-H/CAN-L shorted together high
Gateway module routing CAN messages incorrectly low
CAN terminating resistor (120 Ω) drifted out of spec low

Symptoms

Multiple warning lights may illuminate
Affected modules may go into limp mode or shut down
Specific functions inoperative depending on module
Diagnostic tools may show communication faults

Inspection / repair

Difficulty: hard
DIY: shop recommended
Estimated cost: 60–600 €
Estimated time: 0.8–5 h
Component: low speed can wiring
MIL / check engine light

Sources

Wikipedia · CAN bus

References

sae:J2012 iso:11898