Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 4 (ENGINE CONTROLS - TESTS W/CODES - EEC-IV)
1991 Mercury Tracer Base, 4D Sedan, Automatic
Section 4 (Engine Controls - Tests W/Codes - EEC-IV)
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Section 4 (Engine Controls - Tests W/Codes - EEC-IV)
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1992 Mercury Tracer, 1992 Mercury Topaz, 1992 Mercury Sable, 1992 Mercury Grand Marquis, and 1992 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Self-Diagnostic System
- Quick Test
- Additional System Functions
- EEC-IV Diagnosis By Symptom
- DTC Reference Charts
- Circuit Tests
- Notes
- How To Use Circuit Tests
- Circuit Test Aa - No Start (TFI Ignition Systems)
- Circuit Test Ab - No Start (Dis Ignition Systems)
- Circuit Test Ac - No Start (EDIS Ignition Systems)
- Circuit Test B - Checking Vehicle Battery
- Circuit Test C - Reference Voltage
- Circuit Test DA - Temperature Sensor Test (Act & ECT)
- Circuit Test Db - EGR Temperature (EGRT) Sensor
- Circuit Test Dc - Mass Airflow (MAF) Sensor
- Circuit Test DF - Map/Barometric Pressure (BP) Sensor
- Circuit Test Dg - Knock Sensor (KS)
- Circuit Test DH - Throttle Position Sensor (TPS)
- Circuit Test DL - Pressure Feedback EGR (PFE) Valve, Delta PFE (DPFE) Sensor & EGR Vacuum Regulator (EVR) Solenoid
- Circuit Test DN - EGR Valve Position (EVP) Sensor & EGR Valve Regulator (EVR) Solenoid
- Circuit Test DP - Vehicle Speed Sensor (VSS)
- Circuit Test Dr - Cylinder Identification (CID) Sensor
- Circuit Test DS - Programmable Speedo/Odometer Module (PSOM)
- Circuit Test FD - Brake On-Off (Boo) Switch
- Circuit Test FE - Electrical Load Inputs
- Circuit Test Ff - Power Steering Pressure Switch (PSPS)
- Circuit Test G - MAF/TPS Fuel Injector Pulse Width Test
- Circuit Test H - Fuel Control
- Circuit Test Ha - Adaptive Fuel
- Circuit Test J - Fuel Pump Circuit (Relay & Inertia Switch)
- Circuit Test KA - EGR Vacuum Regulator (EVR) Solenoid
- Circuit Test Kc - Air Management System (Am1/Am2)
- Circuit Test KD - Canister Purge (CANP)
- Circuit Test KE - Idle Speed Control (Air By-Pass)
- Circuit Test KF - Electro Drive Fan (EDF)/High Electro Drive Fan (HEDF)
- Circuit Test Kl - Shift Indicator Light (SIL)
- Circuit Test Km - Wide Open Throttle A/C Cut-Out (WAC) & A/C Demand Switch
- Circuit Test Kn - Fuel Pressure Regulator Control (FPRC) Solenoid
- Circuit Test KP - Octane Adjust
- Circuit Test Kt - Intake Air Control Valve (IAC) System
- Circuit Test M - Dynamic Response Test
- Circuit Test Ml - Self-Test Output (STO) Or Malfunction Indicator Light (Mil)
- Circuit Test NA - TFI Ignition Diagnostic Monitor (IDM)
- Circuit Test NB - Dis Ignition Diagnostic Monitor (IDM)
- Circuit Test NC - EDIS Ignition Diagnostic Monitor (IDM)
- Circuit Test Pa - Spark Timing Check (TFI Vehicles)
- Circuit Test PB - Spark Timing Check (Dis Vehicles)
- Circuit Test Pc - Spark Timing Check (EDIS Vehicles)
- Circuit Test QA - No Codes/Codes Not Listed
- Circuit Test QB - Continuous Memory Code 15 Or 512
- Circuit Test QC - Output State Check Not Functioning
- Circuit Test S - System Check
- Circuit Test Ta - Neutral Drive Input
- Circuit Test Tb - Low & Overdrive Cancel Switch (OCS)
- Circuit Test TC - Transmission Solenoids
- Circuit Test TD - Manual Lever Position (MLP) Sensor
- Circuit Test Te - Transmission Oil Temperature (Tot) Sensor
- Circuit Test TF - Transmission Speed Sensors
- Circuit Test TG - Electronic Transmission Continuous Memory Service Codes
- Circuit Test X - Integral Relay Control Module (IRCM)
- Summary
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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.