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TPI Speed Density Wiring Harness Installation

What You Need
This harness is designed to work with a 1990-1992 style TPI engine and accessory configuration. The 1990-1992 style engine is equipped with the following specific items that my not be found on earlier TPI engines:

  • Small HEI Distributor with Externally Mounted Coil or
  • Large cap with internal coil
  • MAP Sensor (located on passenger side of plenum or on the Firewall) Part # SU105
  • Two Terminal Oil Pressure Switch for 1990 TPI Camaro (Part number PS215) (Corvette #PS168)
  • Speed Density ECM (GM# 1227730) or equivalent  
  • Knock Sensor (different than sensor used with earlier MAF system)

Installing the Harness

Connecting Ignition Power
Connect the big PINK wire labeled, “Ignition on in run and crank”, to an ignition power source that has power with the key in the ON position and in the CRANK position. Be sure your ignition power source can handle 20 amps. If it does not handle 20 amps, you may use a relay (see diagram below).

If Using a Relay
Connect the ignition power from your vehicle (this must supply power with the key in the ON and CRANK position) to the relay's coil high (86), a vehicle ground source to coil low (85), and a battery power source to the relay switch (30). Be sure that the battery power wire can handle 30 amps. If you are unsure, you can run a wire directly from the battery to the relay. Finally, connect the PNK ignition wire in the TPI harness to the relay contact (87). When the relay receives a signal from your vehicle's ignition source, the coil will switch power from the battery to energize the injectors and ECM ignition power.

Ground Wires
All the ground wires are terminated with two ring terminals and can be bolted to the back of the passenger side head. Also be sure to connect a Ground Strap (not included) from the Negative Battery Terminal to the Vehicle's Frame, a Ground Strap from the Vehicle's Frame to the Engine, and a Ground Strap from the Engine to the Vehicle's Body. If your vehicle is not properly grounded in this way, you will have electrical problems.

 Fuel Pump
The ECM sends a signal to the Fuel Pump Relay to turn on the fuel pump. The GRAY wire labeled "Fuel pump Feed+" must be connected to the positive fuel pump power wire to energize the fuel pump. The fuel pump must maintain 37-45 PSI for proper operation.

Electric Fan
The ECM sends a signal to the Fan Relay to turn on the electric fan when the engine reaches the temperature specified in the ECM's PROM. The GREEN/WHITE wire labeled "Fan Relay Trigger" is a trigger wire for a relay only and will not be able to run a fan by itself.

If you are using a Vehicle Speed Sensor (VSS), the GRAY wire labeled "Speed Output 4000 PPM" is an output from the ECM and may be connected to an electronic Speedometer. You must use a Speedometer that requires a 4000 pulse per mile signal. The MAF system uses a speed buffer that takes the speed sensor signal and converts it to A signal that the ECM uses and may not have a speedometer out-put at all. The 1227727 Computer has only 1 output to run an electronic speedometer the wire color is Green/White.

Cruise Control
The RED wire labeled "Speed Output 2000 PPM" may be connected to the Cruise Control Module. This wire sends a 2000 pulse per mile signal from the ECM. This is from the 1227730 computer only

Brake Switch
The PURPLE wire on the 700R4 transmission plug must be connected to the Brake Switch in your vehicle for proper Torque Converter Lockup operation. The PURPLE wire provides 12v ignition power to the Lockup Solenoid inside the 700R4. When the brake pedal is depressed, the brake switch cuts power to the Lockup Solenoid. Power is restored when the brake pedal is not depressed. It is not required to have this active to run and drive the vehicle.

Park/Neutral Indicator Switch
The ORANGE wire coming from the ECM connector, labeled, " Grounded in Park and Neutral", must be connected to a Park/Neutral Indicator Switch. This is not the same as a Neutral Safety Switch. The Park/Neutral Indicator Switch is a switch that lets the ECM know if the vehicle is in Park or Neutral and to adjust the idle accordingly. A Neutral Safety Switch is a switch that prevents the vehicle from starting unless it is in Park or Neutral. This harness is NOT set up with that feature and YOU are responsible for the Neutral Safety feature of your vehicle.  Be sure to connect the ORANGE wire to a Park/Neutral Indicator Switch.

Vehicle Speed Sensor
The Vehicle Speed Sensor connector is included in this harness. However if it doesn’t match then you will need to use an existing connector and splice the PURPLE and the YELLOW wires from the ECM labeled "VSS" to a Vehicle Speed Sensor connector.

Air Conditioning
The input signal wire for the A/C is included in this harness. This DARK GREEN wire lets the ECM know that the A/C is ON by sending 12v when the A/C is ON. If you are not using A/C, you can ignore this wire.

Service Engine Soon
The BROWN wire from the ECM comes out in the multiple wire bundle and is labeled "Service Engine Soon", The brown wire is the light bulb ground. If you provide the bulb and the ignition on power to the bulb, this wire will activate the bulb flashing for trouble codes.




Connecting Ignition Power

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