Engine Controls - Pin Voltage Charts: Introduction

Pin voltage charts are supplied to reduce diagnostic time. Checking pin voltages at ECU determines whether ECU is receiving and transmitting proper voltage signals. Charts may also help determine if ECU harness has an electrical short or open.

NOTE: Unless stated otherwise in testing procedures, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance. Voltage readings may vary slightly due to battery condition or charging rate. Tests are done using Terminal Test Box (VAG 1598).

Fig 1: Identifying ECU Connector Terminals (Typical)

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Fig 2: Terminal Test Box (VAG 1598) & Adapter (VAG 1598-2)

Courtesy of VOLKSWAGEN UNITED STATES, INC.

ECU PIN VOLTAGE (USING TERMINAL TEST BOX (VAG 1598))

Terminals

Component To Be Tested & Condition ⁽¹⁾

Specified Value or Result

18 & 19

Voltage Supply, Ignition Off

Battery Voltage

14 & 35

Voltage Supply, Ignition ON

Battery Voltage

17 & 35

Idle Stabilizer Valve, Ignition ON

Battery Voltage

33 & 19

A/C Compressor On ⁽²⁾

Click From Comp Clutch

19 & 34 (M/T)

Ground To Pin No. 1, Ignition Off

Battery Voltage

34 & 35

Wiring To Starter Lockout Relay, Select "P", Operate Starter

2 Volts Below Battery Voltage

21 & 35

Hall Sender Voltage Supply, Ignition ON

10 Volts Min.

2 & 35

Signal From Speed Sender ⁽³⁾

⁽³⁾

3 & 35

Coolant Temp. Curve ⁽⁴⁾

Voltage Must Lower Uniformly

30 & 35

Signal From Hall Sender, Ignition Off, Operate Starter

⁽⁵⁾ Tester Must Flicker

⁽¹⁾	TESTING CONDITIONS: Disconnect ECU Connector with ignition off. Remove and ground high tension lead (from coil) at distributor cap. Set multimeter to 20-volt DC scale.

⁽²⁾	Jump terminals with jumper wire. DO NOT use multimeter.

⁽³⁾	With Ignition ON and L/F wheel rolled very slowly, approximately every 10-degrees of rotation, voltage will switch from near zero to roughly 10 volts. This is an on-off signal; exact voltages are not critical.

⁽⁴⁾	Start engine cold and allow to warm up while observing multimeter.

⁽⁵⁾	With ignition off, disconnect multimeter and adapters from test box. Disconnect power output stage of ignition coil. Connect LED Tester (US 1115 or VAG 1527B) to test box terminals No. 30 and 35 using Adapter Kit (VW 1594).