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Detroit Diesel DDEC III and IV ECM Vehicle and Engine Connectors

Updated on April 20, 2017

Pinouts, Diagrams, and More for the DDEC 3 and 4

DDEC 3 and DDEC 4 engine computers (Engine Control Modules, ECMs) are used with Detroit Diesel Series 50, 60 and 6V92 engines. These engines are frequently found in buses, boats, motor homes and trucks. The engines differ because Detroit Diesel works with the builder of the vehicle to configure the engine to the builder's application.

Your DDEC 3 or DDEC 4 engine computer has two physical sides to it. One side connects to engine sensors and the other side connects to vehicle sensors and controls.

For example, vehicle sensors include coolant level sensors and even your accelerator.

The engine-side sensors will include connections to things like injectors, oil sensors, and fuel sensors.

This page provides a quick reference to the various pinouts and signals for both the vehicle interface connector and the engine interface connector.

What to Do if Your ECM is Bad?

You may have landed on this page because you're trying to determine if you have a bad engine control module.

In the event that your computer is bad, you have a few options.

  • First, you can try to find a used computer from the exact same make, model and year as your vehicle, and hope that the program in the ECM is truly the same.
  • Second, you can go to an authorized Detroit Diesel Dealer. You can expect to pay upwards of $2,000.
  • Third, you can opt for a third-party outfit that provides rebuilt and reprogrammed ECMs. I've personally been successful using them. Expect to pay about $800 if you go this route.

Location of the Vehicle Connector
Location of the Vehicle Connector

I. Overview of the Vehicle Harness Connector

The Vehicle Interface Connector on the ECM is where the builder of the vehicle provides inputs specific to that vehicle. As mentioned before, these include things like the ignition signal, throttle pedal and coolant level sensors.

That same connector also provides outputs to the vehicle. These outputs include J1939 communications, "check engine" lights, and stop engine lights.

Pins on Vehicle Harness Connector

Vehicle Harness Connector
Vehicle Harness Connector

Above is a view of the vehicle harness connector looking straight at its end after it's been unplugged from the ECM. If you're still having difficulty, orient the little nubs so the the side with eight nubs is to your right.

The wire number, color and function of these pins are identified in the table below.

Pin Numbers on ECM's Vehicle Connector

Vehicle Connector On DDEC ECM
Vehicle Connector On DDEC ECM

These are the pin numbers on the DDEC III and DDEC IV vehicle connector on your ECM. The vehicle harness plugs into this connector. This diagrams what you would see if you looked directly at the connector. Refer to the table below to map these pins to their wire number, color and function.

Vehicle Interface Connector Pin Map

(click column header to sort results)
Cavity  
Wire #  
Color  
Description  
A1
988
Gray
Digital Output
A2
555
Tan
Digital Output
A3
916
Red / Black
Sensor Supply (5V)
B1
419
Purple / White
Check Engine Light (CEL)
B2
509
Purple
Stop Engine Light (SELL)
B3
429
Pink
Ignition
C1
901
Dark Green
Data Link Minus
C2
900
Dark Green / Yellow
Data Link Plus
C3
953
Black
Sensor Return
D1
510
Brown
Variable Speed Governor
D2
417
Dark Blue
Limiting Speed Governor
D3
749
Yellow
Analog Input
E1
451
Light Green
Digital Input
E2
556
Light Blue / Black
Vehicle Speed Plus
E3
557
Light Blue / Orange
Vehicle Speed Minus
F1
542
Yellow
Digital Input
F2
544
Brown / White
Digital Input
F3
499
Light Blue
Digital Output
G1
528
Brown / Red
Digital Input
G2
543
Orange / Black
Digital Input
G3
545
Light Blue
Digital Input
H1
523
Gray / Red
Digital Input
H2
534
Gray
Input
H3
115
Orange
Coolant Level
J1
541
Yellow / Red
Digital Input
J2
531
Orange
Digital Input
J3
906
White
PWM Output
K1
505
Gray
Tachometer Drive
K2
583
Light Blue / Black
Digital Input
K3
979
White
Digital Input

II. The Engine Interface Harness Connector

On the side of the ECM opposite to the vehicle interface connector is the engine interface connector. This looks just like the engine interface connector except that it has been keyed differently to prevent putting the wrong plug into the wrong receptacle.

The engine sensors that connect via this connector give an indication of what the engine is up to. With this information, the ECM decides how to control your engine.

While many of the signals are common from engine to engine, it is important to know that there are others that are specific to an application.

In other words, your engine may or may not use all of the sensors or signals identified in this document.

Engine Harness Connector Pin Locations

DDEC III and IV Engine Harness Connector
DDEC III and IV Engine Harness Connector

You're looking at the end engine harness connector as viewed when directly looking that the pins.

The cavity is the name given to the location where the wires plug in. The wire numbers and colors are generally accurate, but can vary slightly from motor to motor. The same with the description (which describes the function of the wire).

ECM Engine Connector Locations - Pin Numbers

DDEC III and IV ECM Engine Connector
DDEC III and IV ECM Engine Connector

The engine harness connector connects directly to the ECM. This sketch shows the connector on the ECM along with the location of the various pins.

The table below describes what those pins do.

Engine Interface Connector Map

Cavity
Wire Number
Color
Description
L1
904
Purple / White
Barometric Pressure
L2
976
Dark Green
Analog Output #4
L3
925
Dark Blue
J1939 (+)
M1
905
Yellow
Fuel Pressure
M2
958
Blue
Analog Input #5
M3
926
Dark Blue / White
J1939 (-)
N1
906
Orange
Analog Input #3
N2
132
White
Air Temperature
N3
927
White / Blue
J1939 Shield
P1
432
DarkLight Green
Turbo Boost
P2
530
Brown
Fuel Temperature
P3
133
Yellow
Coolant Temp
R1
907
Dark Green
Analog Input #6
R2
120
Tan
Oil Temperature
R3
472
Green
Fuel Temp
S1
112
White
SRS (-)
S2
111
Light Blue
SRS (+)
S3
561
Red
Engine Brake Medium
T1
109
Purple
TRS (-)
T2
110
Dark Green
TRS (+)
T3
562
Orange
Engine Brake Low
W1
416
Gray
Sensor Supply (5VDC)
W2
910
Orange
PWM Output #3
W3
563
Yellow
Digital Output W3
X1
573
Brown
Timed Output
X2
911
Pink
PWM Output #4
X3
564
Tan / Black
Digital Output X3
Y1
909
Light Green / Yellow
PWM Output #2
Y2
452
Black
Sensor Return (Engine)
Y3
565
Red
Digital Output Y3

Thoughts? Comments? Did I Get it Wrong? Let Me Know

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    • profile image

      David 3 weeks ago

      I have troubles with Jake brakes. I want know inputs in the ELM