DTC U0100: Lost Communication with ECM / PCM "A"; DTC U0129: Lost Communication with Brake System Control Module; DTC U0293: Lost Communication with HV ECU [08/2013 - ]: Description

WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

The power management control ECU communicates with the ECM and brake booster with master cylinder assembly (skid control ECU). When the power management control ECU does not receive data from the ECM or brake booster with master cylinder assembly (skid control ECU), the power management control ECU stores DTC U0100 or U0129.
The ECM communicates with the power management control ECU. When the ECM does not receive data from the power management control ECU, the ECM stores DTC U0293.
The brake booster with master cylinder assembly (skid control ECU) communicates with the power management control ECU. When the brake booster with master cylinder assembly (skid control ECU) does not receive data from the power management control ECU, the brake booster with master cylinder assembly (skid control ECU) stores DTC U0293.

DTC No.	DTC Detection Condition	Trouble Area
U0100	The power management control ECU does not receive data from the ECM.	Open or short in sub bus 15 main line or connector Open or short in sub bus 15 branch line or connector Power source circuit of power management control ECU Power management control ECU Power source circuit of ECM ECM Open or short in CAN No. 1 junction connector
U0129	The power management control ECU does not receive data from the brake booster with master cylinder assembly (skid control ECU).	Open or short in sub bus 15 main line or connector Open or short in sub bus 15 branch line or connector Power source circuit of power management control ECU Power management control ECU Power source circuit of brake booster with master cylinder assembly (skid control ECU) Brake booster with master cylinder assembly (skid control ECU) Open or short in CAN No. 1 junction connector
U0293	The ECM does not receive data from the power management control ECU. The brake booster with master cylinder assembly (skid control ECU) does not receive data from the power management control ECU.	Open or short in sub bus 15 main line or connector Open or short in sub bus 15 branch line or connector Power source circuit of ECM ECM Power source circuit of power management control ECU Power management control ECU Power source circuit of brake booster with master cylinder assembly (skid control ECU) Brake booster with master cylinder assembly (skid control ECU) Open or short in CAN No. 1 junction connector

HINT:

This diagnosis procedure is for when DTC U0100, U0129 and U0293 are output at the same time.