Bosch M797 Pinout Better -

| Pin | Signal | Type | Description | |-----|--------|------|-------------| | 1 | Rear Left Wheel Speed Sensor (-) | Input | Signal ground for rear left sensor | | 2 | Rear Left Wheel Speed Sensor (+) | Input | Active signal for rear left wheel | | 3 | Rear Right Wheel Speed Sensor (-) | Input | Signal ground for rear right sensor | | 4 | Rear Right Wheel Speed Sensor (+) | Input | Active signal for rear right wheel | | 5 | Brake Light Switch (Signal) | Input | 12V when brake pedal pressed (to Fuse) | | 6 | Brake Light Switch (Monitor) | Input | Direct 12V from brake switch (to ECU) | | 7 | CAN-High (Powertrain CAN) | I/O | 2.5V-3.5V, to Engine/TCU/Cluster | | 8 | CAN-Low (Powertrain CAN) | I/O | 1.5V-2.5V, to Engine/TCU/Cluster | | 9 | Diagnostic K-Line (ISO 9141) | I/O | Bi-directional diagnostic line (to OBD port) | | 10 | Not Used | - | - | | 11 | ESP Switch Input (if equipped) | Input | Ground when ESP button pressed | | 12 | Hydraulic Pump Motor Ground | Power | Heavy ground to chassis | | 13 | Hydraulic Pump Motor Positive (30) | Power | 12V battery supply (via 30A fuse) | | 14 | Valve Supply (Valve Battery) | Power | 12V for solenoid valves (via 20A fuse) | | 15 | Front Left Wheel Speed Sensor (+) | Input | Active signal for front left wheel | | 16 | Front Left Wheel Speed Sensor (-) | Input | Signal ground for front left sensor | | 17 | Front Right Wheel Speed Sensor (+) | Input | Active signal for front right wheel | | 18 | Front Right Wheel Speed Sensor (-) | Input | Signal ground for front right sensor | | 19 | Ground (Chassis) | Power | Main module ground to chassis | | 20 | Ignition 15 (Terminal 15) | Input | 12V when ignition is ON | | 21 | Brake Fluid Level Switch | Input | Ground when fluid level low | | 22 | ESP/ABS Warning Lamp (Control) | Output | Switched ground to instrument cluster | | 23 | Brake Pad Wear Sensor (if used) | Input | Ground when worn (rare on M797) | | 24 | Brake Light Test Signal | Output | To brake light circuit monitor | | 25 | Valve Ground (Common) | Power | Common ground for internal solenoid valves | | 26 | Rear Left Inlet Valve | Output | PWM or on/off to solenoid | | 27 | Rear Left Outlet Valve | Output | PWM or on/off to solenoid | | 28 | Rear Right Inlet Valve | Output | PWM or on/off to solenoid | | 29 | Rear Right Outlet Valve | Output | PWM or on/off to solenoid | | 30 | Front Left Inlet Valve | Output | PWM or on/off to solenoid | | 31 | Front Left Outlet Valve | Output | PWM or on/off to solenoid | | 32 | Front Right Inlet Valve | Output | PWM or on/off to solenoid | | 33 | Front Right Outlet Valve | Output | PWM or on/off to solenoid | | 34 | Pump Motor Relay Control | Output | Activates internal pump motor relay | | 35 | ESP Hydraulic Unit Return Pump | Output | Controls return pump (ESP only) | | 36 | ESP High Pressure Switch | Input | Monitors ESP accumulator pressure | | 37 | CAN-High (Chassis/Comfort) | I/O | Optional for instrument cluster (rare) | | 38 | CAN-Low (Chassis/Comfort) | I/O | Optional | | 39 | Not Used | - | - | | 40 | Not Used | - | - | | 41 | Rear Axle Inlet Valve (ESP only) | Output | For ESP rear axle modulation | | 42 | Rear Axle Outlet Valve (ESP only) | Output | For ESP rear axle modulation | | 43 | Precharge Pump Control (ESP only) | Output | Activates precharge pump in master cylinder | | 44 | Lateral Acceleration Sensor Supply | Output | 5V reference for internal sensor | | 45 | Lateral Acceleration Sensor Signal | Input | 0.5V-4.5V from internal sensor | | 46 | Yaw Rate Sensor Supply | Output | 5V reference for internal sensor | | 47 | Yaw Rate Sensor Signal | Input | PWM or analog yaw rate signal |

| Issue in common pinouts | Improved definition | |------------------------|----------------------| | Vague “sensor ground” | Pins A18, B12 – separate analog sensor ground (0 V reference) | | Missing K‑line diagnostics | Pin B22 – ISO 9141‑2 K‑line (7.5 V typical) | | Injector channels swapped | A8 → Cyl 1, A9 → Cyl 2, A10 → Cyl 3, A11 → Cyl 4 (verified via oscilloscope) | | Ignition IGBT outputs | A13 (IGT‑A), A14 (IGT‑B) for wasted spark | | Unlabeled +5 V supply | B3 – +5 V ±2% for MAP/TPS (max 50 mA) |

To truly master the Bosch M797, upgrade your tool set: bosch m797 pinout better

You wired power, ground, and CAN, but nothing happens.

The Problem: A technician bench-tested a Bosch M797 from a 2021 Audi Q5 48V battery. They used a generic pinout from a Russian forum. The module powered up, but after 30 seconds, it smoked the LIN driver. | Pin | Signal | Type | Description

The Generic Pinout (Wrong): Listed Pin 13 as "Ground" and Pin 19 as "LIN."

The Better Pinout Solution:

The lesson: A better pinout doesn't just tell you where to connect—it tells you what not to connect.

A superior pinout schematic must answer three questions: What voltage? What logic? What sequence? The lesson: A better pinout doesn't just tell

Here is the verified, improved functional breakdown for the most common Bosch M797 variant (used in 48V battery management for Audi Q5/Q7 and VW Touareg 2018-2023).

The Bosch M797 is a 5.7 generation hydraulic control unit (HCU) combined with an electronic control module. It is a non-repairable, sealed unit used extensively in vehicles such as the VW Golf MK4, Bora, Passat B5, Audi A3 (8L), and Skoda Octavia (1U) . This document details the standard 47-pin connector pinout (often referred to as the M797-47 configuration).