1989 Ford Probe GL, AutomaticFACTORY OEM SERVICE PROCEDURE

How To Use Circuit Tests

  1. DO NOT  perform any CIRCUIT TEST unless directed to do so by a QUICK TEST procedure. Ensure all non-EEC related faults are corrected. FOLLOW EACH TEST STEP IN ORDER UNTIL FAULT IS FOUND. DO NOT  replace any part unless directed to do so. When more than one service code is received, start with the first code displayed.
  2. CIRCUIT TESTS require that you prove the electrical circuits are okay before you replace sensors or any other components. Always test circuits for continuity between the sensor and the ECA. Test all circuits for shorts to power, opens, or shorts to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with KOEO or as specified in CIRCUIT TESTS.
  3. DO NOT  measure voltage or resistance at ECA or connect any test light, unless specified in testing procedure. DO NOT  pierce wiring. If backprobing is specified, always backprobe harness side of connector, never the connector side. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless specified.
  4. An open circuit is defined as a circuit which has a resistance of greater than 5 ohms, unless otherwise specified. Disconnect solenoids and switches before checking circuit continuity or energizing solenoids.
  5. A short is defined as any resistance to ground of less than 10,000 ohms, unless otherwise specified.
    NOTE: CIRCUIT TESTS are grouped in the following categories.
    • A1-A3 Preliminary Tests
    • B1-B16 Input Sensor Tests
    • C1-C3 Fuel Control Systems
    • D1-D11 ECA Output Tests
      NOTE: In the following tests, circuits and illustrations are supplied courtesy of Ford Motor Co. Complete EEC system wiring diagrams may be found at the end of this article. The abbreviations for wire colors used in the individual CIRCUIT TEST diagrams are as follows:
    • "BK" Black
    • "BL" Blue
    • "BR" Brown
    • "DB" Dark Blue
    • "DG" Dark Green
    • "GY" Gray
    • "GN" Green
    • "LB" Light Blue
    • "LG" Light Green
    • "N" Natural
    • "O" Orange
    • "PK" Pink
    • "P" Purple
    • "R" Red
    • "T" Tan
    • "W" White
    • "Y" Yellow
SERVICE CODE TO CIRCUIT TEST REFERENCE CHART

Diagnostic Service Code Circuit Test Non-Turbo Engine Circuit Test Turbo Engine
No Codes or "00" Go To Next Quick Test Go To Next Quick Test
"01" A1 A1
"02" N/A N/A
"03 N/A N/A
"04" N/A N/A
"05" N/A B4
"08" B6 B6
"09" B2 B2
"10" B1 B1
"12" B5 B5
"14" B3 B3
"15" D3 D3
"16" B9 B9
"17" D3 C1
"25" D7 D7
"26" D2 D2
"28" D1 D1
"29" N/A N/A
"34" D3 D3
"42" N/A D5
No Codes With "Check Engine"Light On or Low Voltage at STO. Terminal D9 D9
Codes Not Listed D10 D10
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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