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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.
Fig 1: Identifying ECU Connector Terminals (Typical)
G121509Courtesy of VOLKSWAGEN UNITED STATES, INC.
VOLTAGE CHECKS (DIGIFANT I) VAG 1598

Pins Component To Be Tested & Condition (1) Specification
" ECU NOT CONNECTED TO VAG 1598 "
1 & 19 Voltage To Control Unit, Ign. On Battery Voltage
19 & 35 Voltage To Control Unit, Ign. On Battery Voltage
1 & 6 Wires To Coil, Ign. On Battery Voltage
1 & 4 CHECK ENGINE Light, Ign. On Battery Voltage
1 & 23 Idle Stabilizer Valve, Ign. On Battery Voltage
1 & 24 (Jumper) Wires To Fuel Pump Relay, Ign. On " Pumps Must Run Audibly
1 & 20 Cyl. 1 Fuel Injector, Ign. On Battery Voltage
1 & 21 Cyl. 2 Fuel Injector, Ign. On Battery Voltage
1 & 3 Cyl. 3 Fuel Injector, Ign. On Battery Voltage
1 & 2 Cyl. 4 Fuel Injector, Ign. On Battery Voltage
1 & 25 (M/T) Wiring To Starter Terminal 50, Operate Starter, Then Turn Ign. Off 8 Volts Minimum
11 & 28 Coolant Temperature Sensor, (1) (1)
28 & 30 Intake Air Temperature Sensor, (1) (1)
17 & 36 Diagnostic Connector Circuit, Jumper White Connector Term. 1.5 Ohms Maximum
15 & 28 Airflow Potentiometer, Ign. Off 500-1000 Ohms
13 & 15 Airflow Potentiometer, Move Airflow Flap Or Operate Starter Change In Resistance
1 (2) & 34 Throttle Potentiometer Circuit, 3-Pin Connector Disconnected 1.5 Ohms Maximum
2 (2) & 33 Throttle Potentiometer Circuit, 3-Pin Connector Disconnected 1.5 Ohms Maximum
3 (2) & 28 Throttle Potentiometer Circuit, 3-Pin Connector Disconnected 1.5 Ohms Maximum
1 (2) & 28 Hall Sender Circuit, Harness Connector Disconnected 1.5 Ohms Maximum
2 (2) & 37 Hall Sender Circuit, Harness Connector Disconnected 1.5 Ohms Maximum
3 (2) & 38 Hall Sender Circuit, Harness Connector Disconnected 1.5 Ohms Maximum
1 & 2 (2) O2 Sensor Circuit, Harness Connector Disconnected 1.5 Ohms Maximum
3 (3) & 16 O2 Sensor Circuit, Harness Connector Disconnected 1.5 Ohms Maximum
3 (3) & 9 O2 Sensor Circuit, Harness Connector Disconnected Infinity
1 & 16 O2 Sensor Circuit, Harness Connector Reconnected Infinity
32 & Grn Wire A/C Compressor Wiring, Disconnect 1-Pin Connector 1.5 Ohms Maximum
" ECU CONNECTED TO VAG 1598 "
28 & 34 " Throttle Potentiometer (Power), (3) Ign. On 4.5-5.5 Volts "
28 & 33 Throttle Positioner, Ign. On "
" Idle 0.3-1.7 Volts
" Full Throttle 3-5 Volts
28 & 38 (4) Hall Sender (Voltage), Ign. On .10 Volts Minimum
37 & 38 (4) Hall Sender (Signal), Operate Starter " LED Must Flicker
1 & 6 (4) " Ign. Signal Function, Operate Starter " LED Must Flicker
(1) Refer to I - SYS/COMP TESTS or K - SENSOR OPERATING RANGE CHARTS article.
(2) Terminal number indicated is the component's connector terminal number and not of ECU or Test Box.
(3) Potentiometer harness connector disconnected and tested with ignition on.
(4) Perform test only if engine will not start. Turn ignition off. Instead of multimeter, connect LED Tester (US 1115) using Adapter Kit (VW 1594). Disconnect harness from fuel rail (main injector connector).
VOLTAGE CHECKS (FOX - DIGIFANT II) VAG 1598

Pins Component To Be Tested & Condition (1) Specification
13 & 14 Voltage To Control Unit, Ign. On Battery Voltage
14 & 19 Voltage To Control Unit, Ign. On Battery Voltage
1 & 13 " Wire To Starter Terminal 50, Operate Starter 8 Volts Minimum
5 & 12 " Fuel Injectors, 6-Pin Connector Disconnected 3.7-5.0 Ohms "
6 & 25 " Hall Sender Control Unit, Harness Disconnected Continuity "
6 & 11 Coolant Temperature Sensor, (2) (2)
6 & 17 Airflow Potentiometer, Ign. Off 500-1000 Ohms
17 & 21 " Airflow Potentiometer, Move Airflow Sensor Flap Resistance Change
6 & 9 Intake Air Temp. Sensor, (2) (2)
3 & 13 " Fuel Pump Relay Circuit, Ign. On " Fuel Pump Must Operate
6 & 8 " Hall Sender Ckt, Harness Disconnected & 3 Wire, In Connector Jumpered Continuity "
6 & 18 " Hall Sender Circuit, Harness Disconnected & 3 Wire, In Connector Jumpered Continuity "
2 & 13 O2 Sensor Circuit (3) Continuity
(1) TEST CONDITIONS: Turn ignition off. Disconnect harness connector from ECU. Connect Test Box (VAG 1598) to ECU harness connector using Adaptor Cable (VAG 1598/2), leaving
(2) Refer to I - SYS/COMP TESTS or K - SENSOR OPERATING RANGE CHARTS article.
(3) O2 Sensor harness connector disconnected and harness terminal 4 jumpered to ground.
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