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Engine Controls - Pin Voltage Charts: Introduction

Pin voltage charts are supplied to reduce diagnostic time. Checking pin voltages at the DME/Motronic control unit determines whether it is receiving and transmitting proper voltage signals. Charts may also help determine if control unit wiring harness is shorted or opened.

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.
DME/MOTRONIC CONTROL UNIT PIN ASSIGNMENTS (1) (2.5L M50 - DME 3.3.1)

Pin No. Function/Description Signal Type Or Voltage Value
1 Fuel Pump Relay Ground Circuit Term. 85
2 Idle Speed Control Valve (Close) Zero Volts Or Ground (Output Signal)
3 Fuel Injector (No. 5) Pulse (Duty Cycle) Duration In % Output Signal)
4 Fuel Injector (No. 6) Pulse (Duty Cycle) Duration In % (Output Signal)
5 Fuel Injector (No. 4) Pulse (Duty Cycle) Duration In % (Output Signal)
6 Fuel Injectors (Ground) Ground Circuit
7 Camshaft Actuator (VANOS) Ground Circuit (Output Signal)
8 CHECK ENGINE Light (2) Ground Circuit (Output Signal)
11 Potentiometer Electronic Transmission
Control (EGS) Square Wave Output Signal
13 Oxygen Sensor PCM Monitored (5 Volt) Signal Circuit
14 Air Mass Sensor Ground Circuit
15 Ground Grounding Circuit
16 Crankshaft Sensor Input Signal (Inductive)
17 Camshaft Position Sensor Hall-Effect Signal
23 Ignition Coil (Cylinder No. 4) Primary Circuit Output Signal
24 Ignition Coil (Cylinder No. 6) Primary Circuit Output Signal
25 Ignition Coil (Cylinder No. 5) Primary Circuit Output Signal
26 Battery Voltage (Permanent (3) 12 Volts (Battery Voltage Input)
27 DME Master Relay (4) Output Signal
28 Sensors (Shield Wire) Ground Circuit
29 Idle Speed Control Valve (Open) Zero Volts Or Ground (Output Signal)
31 Fuel Injector (No. 3) Pulse (Duty Cycle) Duration In % (Output Signal)
32 Fuel Injector (No. 2) Pulse (Duty Cycle) Duration In % (Output Signal)
33 Fuel Injector (No. 1) Pulse (Duty Cycle) Duration In % (Output Signal)
34 Ground (Except Injectors & Ignition) Ground Circuit
36 Fuel Tank Vent (Evaporation) Control (5) Pulse (Duty Cycle) Duration In % (Output Signal)
38 Oxygen Sensor Heater Relay Output Signal (With Ignition On)
40 Oxygen Sensor Signal Sensor Ground Circuit
41 Air Mass Sensor 0-5 Volts Input Signal
42 Vehicle Speed Signal Square Wave Input Signal
43 Crankshaft Sensor/RPM Signal Input Signal (Inductive)
44 Engine Sensors (Ground) Ground Circuit
45 Shield Ground Ground Circuit
46 Instrument Cluster (Fuel Consumption) Square Wave Output Signal
47 Engine Speed Signal Ignition Interval (TD) Output Signal
48 A/C Compressor Shutoff (6) Output Signal
50 Ignition Coil (Cylinder No. 1) Primary Circuit Output Signal
51 Ignition Coil (Cylinder No. 2) Primary Circuit Output Signal
52 Ignition Coil (Cylinder No. 3) Primary Circuit Output Signal
54 Battery Voltage (3) 12 Volts (Battery Voltage Input)
55 Ignition (Ground) Ground Circuit
56 Start (Ignition) Input 12 Volts (Battery Voltage Input)
57 Ignition Timing Intervention Transmission Module Circuit (Input Signal)
59 Throttle Position Sensor 5-Volt (Reference) Output Signal
60 Programming Voltage (7) Voltage (Input Signal)
64 A/C Switch (8) 12 Volts (Battery Voltage Input)
65 A/C Pressure Signal Input Signal
66 Anti-Theft Alarm Switch (9) 12 Volts (Battery Voltage Input)
69 Knock Sensor (No. 4-6) Input Signal
70 Knock Sensor (No. 1-3) Input Signal
71 Knock Sensor (Ground) Ground Circuit
73 T1rottle Potentiometer (TPS) (10) 0.5-5.0 Volts (Input Signal)
77 Intake Air Temperature Sensor 0-5 Volts (Input Signal)
78 Engine (Coolant) Temperature Sensor 0-5 Volts (Input Signal)
81 Park/Neutral Switch (11) Input Signal
87 Diagnostic Initiation Line (RxD) (12) 12 Volts (Battery Voltage Input)
88 Diagnostic Data Line (TxD) (12) Input/Output Signal
(1) Pin assignments not listed are not used (blank).
(2) In case of defect, check CHECK ENGINE light function.
(3) No DME functions if voltage is not present.
(4) No DME functions when master relay is off. Connect jumper wire between terminals No. 30 and 87.
(5) Duty cycle depends on engine speed and load.
(6) Output signal to A/C relay only at speed of 5 MPH and engine at full load.
(7) Only activated during programming.
(8) With A/C system on.
(9) With anti-theft alarm activated (armed).
(10) Voltage signal input to control unit will vary depending on throttle position.
(11) Gear selector lever in Park or Neutral position.
(12) With diagnostic socket cover closed.
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