1G The 1990 Engine Control Wiring Harness

*****IMPORTANT*****​

Note that the wire color layout diagrams accompanying each picture are as seen FROM the CONTROL HARNESS SIDE of the connector with the release tab (for a male side connector) or locking notch (for a female side connector) on top. That is, you are looking at the wires going into the connector, OPPOSITE the side that is pictured. Like this: How to identify ECU pin numbers.

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This is the ENGINE CONTROL harness. If you want information on the ENGINE COMPARTMENT harness, see: The 1990 Engine COMPARTMENT Wiring Harness.

As we all know, the 1990 model year had many quirks to it when compared to the later model 1Gs. Because this was a single (and the first) year of the Eclipse/Talon/Laser trio, information on these cars isn't nearly as abundant as 1991-1994 models.

I don't plan to dive into and explain the differences between these models as there are plenty of threads around naming the differences. In short, this article is a configuration diagram. It aims to familiarize members with the 1990 4G63 turbo engine control harness electrical connections, similar to what snowborder714 did in his 2g Engine Bay Electrical Connections article, but not nearly as thorough. To be clear, this article does not cover every electrical connection in the 1990 engine bay, only those on the engine control harness, including the handful of interior connections. For your convenience, the 1991 configuration diagrams are provided.

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As a couple extras, it will touch on some connector differences that must be attended to when swapping a 1990 turbo engine control harness into a later model 1G or vice versa (these are denoted by **). It lists original wire colors and original individual wire locations as viewed from the wire side of the connector as well as a visual of each connector on the harness.

Also, for comparison, here is a similar page for the later model 1Gs (those connectors labeled with * are either completely different, in a different location, or non-existent on the later model 1Gs): 1Gb DSM 4G63 Turbo Wiring Harness Diagram

First and foremost, the main harness itself. The alphanumeric identifiers relate to those in the 1991 configuration diagram found in the electronic copy of the factory service manual: Download the 1G Service Manuals. The harness displayed here is a 1990 turbo engine harness which, by consequence, means it is from a vehicle with a manual transmission.

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A-08: Dual Pressure Switch (black connector, 2-pin)
A-09: Wiper Motor (black connector, wide rectangular 4-pin)
A-10: Control Wiring Harness and Battery Cable Assembly Combination / Starter Wiring Harness and Reverse Light Switch (black connector, square 4-pin)
*A-11: Auto-Cruise Control Actuator (black connector, square 4-pin)
A-12: Brake Fluid Level Sensor (black connector, stacked 2-pin)
A-13: Control Wiring Harness and Solenoid Valve Harness Assembly Combination (black connector, rectangular 6-pin)
A-36: Air Flow Sensor (black connector, NT 6-pin, Turbo 8-pin)
A-51: Waste Gate Solenoid (black connector, stacked 2-pin)
A-52: Control Wiring Harness and Engine Compartment Wiring Harness Combination (black connector, wide rectangular 4-pin)
A-53: Control Wiring Harness and Engine Compartment Wiring harness Combination (black connector, large 1-pin)
A-55: Fuel Pump Check Connector (black connector, small 1-pin)
A-56: Noise Condenser (black connector, very small 1-pin)
A-57: Defogger Relay (black connector, 5-pin)
A-58: Injector Resistor Pack (black connector, rectangular 6-pin)
A-59: Engine Speed Adjustment Connector (black connector, small 1-pin)
A-60: Ignition Timing Adjustment Connector (black connector, 2-pin)

*B-00: Noise Filter (for Tachometer) (black connector, stacked 2-pin)
B-01: Injector No. 4 (black connector, 2-pin)
*B-02 & B-05: Throttle Position Sensor and Idle Switch (black connector, square 4-pin)
**B-04: Idle Speed Control Actuator (black connector, rectangular 6-pin)
B-06: Injector No. 3 (black connector, 2-pin)
B-07: Detonation (Knock) Sensor (grey / gray connector, 2-pin)
B-08: EGR Temperature Sensor (black connector, 2-pin)
B-09: Injector No. 2 (black connector, 2-pin)
B-10: Injector No. 1 (black connector, 2-pin)
*B-14: Ignition Coil (Coil Pack) (black connector, square 4-pin)
*B-15: Power Transistor Unit (black connector, straight 6-pin)
B-16: A/C Magnetic Clutch (black connector, round 1-pin)
B-26: Oxygen (O2, 02) Sensor (black connector, round 4-pin)
B-29: Engine Coolant Temperature Gauge Unit (black connector, small 1-pin)
B-30: Engine Coolant Temperature Sensor (for ECU) (black connector, stacked 2-pin)
B-31: Engine Coolant Temperature Switch (for A/C) (black connector, 2-pin)
*B-32: Crank Angle and Top Dead Center Sensor (Cam Angle Sensor, CAS) (black connector, square 4-pin)

C-56: Oxygen (O2, 02) Sensor Check Connector (milk white connector, small 1-pin)
C-57: Control Wiring Harness and Body Wiring Harness Combination (milk white connector, 1-pin, passenger side kick panel)
**C-58: Control Wiring Harness and Body Wiring Harness Combination (white connector, 16-pin, passenger side kick panel)
C-59: Control Wiring Harness and Body Wiring Harness Combination (milk white connector, 6-pin, passenger side kick panel)
C-63: MPI Control Relay (milk white connector, 10-pin)
C-64: MPI Control Unit (ECU, small connector) (yellow connector, 10-pin)
C-65: MPI Control Unit (ECU, medium connector) (yellow connector, 18-pin)
**C-66: MPI Control Unit (ECU, large connector) (yellow connector, 24-pin)
**C-67: Control Wiring Harness and Body Wiring Harness Combination (under center console) (white connector, 8-pin)

The wire color layout diagrams accompanying each picture are as seen FROM the HARNESS SIDE of the connector with the release tab (for a male side connector) or locking notch (for a female side connector) on top. They should be color coded correctly, but if there is a disagreement with the letters and the color of the letters, go by the letters. When two colors are listed together, the first is the main color and the second is the color of the stripe or tracer. The letters represent the following colors:

B - Black
W - White
R - Red
G - Green
L - Blue
Y - Yellow
O - Orange
Lg – Light Green

PM me if you find any errors and I will make corrections as necessary.

Finally, the following supporting vendors supply the individual connectors linked or partial kits for different model year DSMs:
JNZ Tuning
Extreme PSI
Magnus Motorsports

At the end of the day, they are all coming from Sheridan Engineering.

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To relate wire sizes from your FSM (metric) to AWG sizes: The Engineering Toolbox - Wire Gauge Converter.

 

[19Eclipse90]

A-08: Dual Pressure Switch

Connector available at CON-ACTEMP

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[19Eclipse90]

A-09: Wiper Motor

Connector available at: DSD04 F.

 

[19Eclipse90]

A-10: Control Wiring Harness and Battery Cable Assembly Combination / Starter Wiring Harness and Reverse Light Switch

The two black w/ yellow wires are involved in the starting circuit and run to the starter motor/solenoid. The red and red w/ blue wire are for the reverse lights sensor.

Connector available at: NMWP 4P Female.

Here's the whole starter harness... A-10 is the connection to the rest of the harness. B-23 is the reverse light switch connector.

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The reverse lights switch is available at NMWP2F-B.

**Kudos to @Spector5 for catching my error on the starter harness. Correct image is shown.

 

[19Eclipse90]

*A-11: Auto-Cruise Control Actuator

One of the "mystery" connectors that seems to come up relatively frequently, 1990 models had the cruise control unit in front of the battery instead of on the firewall like the 1991+ models. It is also of note that the 1990 cruise control is mechanically actuated and does not use vacuum.

Connector available at: NMWP 4P Female.

 

[19Eclipse90]

A-12: Brake Fluid Level Sensor

Connector available at: DSD02 F.

 

[19Eclipse90]

A-13: Control Wiring Harness and Solenoid Valve Harness Assembly Combination

Connector available at: NMWP 6P Female.

Have this open and want to seal it up? Use this male connector to protect it from the elements! See: NMWP 6P Male.

 

[19Eclipse90]

A-36: Air Flow Sensor

The picture below is for a turbo MAF. A non-turbo harness has only six wires (in two rows of three) running to it -- the one that will not be present is the green with white stripe which runs to pin 14 on C-66.

1G turbo MAF connector available at: NMWP 8P female.

1G non-turbo MAF connector available at: NMWP 6P Female.

Interested in upgrading to a 2G MAF and don't have the connector? See: CON-2GMAF-8F.

For reference, non-turbo MAF pin-out:

Pin 1 - Green with blue stripe, to ECU pin 10
Pin 2 - Red, sensor power wire
Pin 3 - Green with red stripe, to ECU pin 23 and Throttle Position Sensor pin 1
Pin 4 - Green with black stripe, to ECU pins 17 and 24
Pin 5 - Green with yellow stripe, to ECU pin 16
Pin 6 - Green with orange stripe, to ECU pin 8​

Turbo MAF pin-out:

Pin 1 - Green with white stripe, to ECU pin 14 for '90 ECU........ [or ECU pin 6 for '91+ ECU]
Pin 2 - Green with blue stripe, to ECU pin 10
Pin 3 - Red, sensor power wire
Pin 4 - Green with red stripe, to ECU pin 23 and Throttle Position Sensor pin 1
Pin 5 - Empty
Pin 6 - Green with black stripe, to ECU pins 17 and 24
Pin 7 - Green with yellow stripe, to ECU pin 16
Pin 8 - Green with orange stripe, to ECU pin 8​

 

[19Eclipse90]

A-51: Waste Gate Solenoid

1G ECU Pinouts

ERROR: Note that the "yellow" wire is actually ORANGE and runs to pin 105 of the ECU.

Connector available at: DSD02 F.

 

[19Eclipse90]

A-52: Control Wiring Harness and Engine Compartment Wiring Harness Combination

Connector available at: DSD04 F.

This is one of the connectors that joins the Engine CONTROL Wiring Harness with the Engine COMPARTMENT Wiring Harness. Specifically, it joins with this connection: The 1990 Engine COMPARTMENT Wiring Harness.

NOTE: This is one of the connections UNDERNEATH the fuse box; there are no connections running to the fuse box itself.

 

[19Eclipse90]

A-53: Control Wiring Harness and Engine Compartment Wiring harness Combination

This is one of the connections that join this harness and the engine control harness together. Specifically, it joins with this connection on the Engine Control Wiring Harness: The 1990 Engine COMPARTMENT Wiring Harness.

NOTE: This is one of the connections UNDERNEATH the fuse box; there are no connections running to the fuse box itself.

Connector available at: 1G 312 F

 

[19Eclipse90]

A-55: Fuel Pump Check Connector

Just a short note of interest for you folks with a 1991 engine harness: 1g base timeing/confusing.

Also there are 91's where the fuel pump connector was omitted from the harness. There is a TSB on the issue.

Connector available at: DSD01 F.

 

[19Eclipse90]

A-56: Noise Condenser

 

[19Eclipse90]

A-57: Defogger Relay

 

[19Eclipse90]

A-58: Injector Resistor Pack

Note that this is a turbo car item only. Make sure not to confuse it with B-04: Idle Speed Control Actuator.

An easy way to tell visually, is that the inector resistor connector should have 5 wires on both sides of the connector, and 1 empty spot. The ISC should have all 6 wires.

Connector available at: NMWP 6P Female.

The mating connector for the injector restistor pack is available at: NMWP 6P Male.

 

[19Eclipse90]

A-59: Engine Speed Adjustment Connector

Connector available at: DSD01 F.

 

[19Eclipse90]

A-60: Ignition Timing Adjustment Connector

The connector that would seal this up is available at: NMWP 2P B Female.

The harness connector is available at: NMWP 2P Male.

 

[19Eclipse90]

B-00: Noise Filter (for Tachometer)

For good measure, you can check this link to see what, exactly, connects here. If the NOISE FILTER is missing, your 1990 tachometer will not work. These are some different versions of the noise filter:

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Note that the 1990 tachometer receives its signal from the tachometer gate interface module that is attached to the coil pack. The signal is output to the white wire at pin 3. This is the tacho interface: Stock tach doesnt work, but tach works on SAFC

Also for reference:
Lil Evo Tachometer Fix
help with tach

The OEM part number for the noise filter is MB542494. Whether or not you can find them new again is completely up to you.

Fortunately, there are ways to get around having the OEM filter. For you DIY’ers, here are a couple threads where the innards of the nose filter are defined and dissected:
1G Tach Question
90 Tach Filter Hacked Up

TIP: After numerous trips to the junkyard, I've collected a small supply of these noise filters. They all work as I have tried them on my own vehicle. The kicker is that they are not all from 1990 model 1Gs. A couple of them were pulled from late 80's/early 90's model Colts. These filters are mounted by one M6 (that's a 10mm head) bolt. They have the same shape connector on them as the 1990 unit. Something else I found is that, in order for the noise filter to work correctly, the filter body (or mounting bracket, as is the case for the Colt style filter) must be grounded to something (the intake manifold is my choice location). If this is not done, the tachometer will jump around and tends to get stuck around 3000rpm. The Colt part number is MB627900 or MB627901, depending on options; either should work. Having said that, I wouldn't expect them to be any cheaper new than the 1G units, if you can find them

Semi-related find: Pulled a noise filter from a 1990 Hyundai Excel and it also does the trick.

Connector available at: DSD02 F.

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[19Eclipse90]

B-01: Injector No. 4

Connector available at: JFC 2P.

 

[19Eclipse90]

B-02 & B-05: Throttle Position Sensor and Idle Switch

The 1990 model integrated the idle switch into the throttle position sensor connector. When using a 1991+ throttle body, the green wire in the dotted box would need to run to the idle switch. For a write up on this site: 1990 Swap to 91-94 Throttle Body

The 1990 harness side TPS connector is available at: NMWP 4P Male.

The 1990 sensor side TPS connector is available at: NMWP 4P Female.

The 1991+ TPS connector is available at: JFC 4PB .

 

[19Eclipse90]

**B-04: Idle Speed Control Actuator

Make sure not to confuse this with A-58: Injector Resistor Pack on a turbo vehicle.

An easy way to tell visually, is that the injector resistor connector should have 5 wires on both sides of the connector, and 1 empty spot. The ISC should have all 6 wires.

ERROR: The wire colors orientation shown here is as found in '91+ vehicles. In a '90 vehicle, the white and black wire are swapped; pin 4 is the white and pin 6 is the black. See this post and the one following it: 91 iac in 90, looking for the ecu pinouts between 90/91. As a work around solution, see: 1990 ISC motor – reverse polarity for new part?.

The ISC actuator motor harness connector is available at: NMWP 6P Female.

The mating connector for the ISC actuator motor is available at: NMWP 6P Male.

 

[19Eclipse90]

B-06: Injector No. 3

Connector available at: 18. - JFC 2P.

 

[19Eclipse90]

B-07: Detonation (Knock) Sensor

Note the color ( gray ) of this connector / connection / plug; it is the same for all turbo DSMs and is the only connector of this color in the 1G engine compartment.

Connector available at: NMWP 2P GY female.

 

[19Eclipse90]

B-08: EGR Temperature Sensor

Connector available at: NMWP 2P B Female.

 

[19Eclipse90]

B-09: Injector No. 2

Connector available at: JFC 2P.