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 30 (ENGINE CONTROLS - TESTS W/CODES - EEC-IV (3.0L))
1991 Mercury Tracer Base, 4D Sedan, Automatic
Section 30 (Engine Controls - Tests W/Codes - EEC-IV (3.0L))
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Section 30 (Engine Controls - Tests W/Codes - EEC-IV (3.0L))
WARNING: This page is about a different car, the 1994 Mercury Topaz, 1994 Mercury Sable, 1994 Ford Tempo, and 1994 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Self-Diagnostic System
- Quick Test
- Additional System Functions
- Service Code-To-Test Reference Menus
- Diagnostic Trouble Code Definition Charts
- Circuit Tests
- Notes
- How To Use Circuit Tests
- Circuit Test Aa - No-Start - Di - Dist Ignition Systems
- Circuit Test Ab - No-Start EI - DISTRIBUTORLESS Ignition Systems (Low Data Rate)
- Circuit Test Ac - No-Start - EI - DISTRIBUTORLESS Ignition Systems (High Data Rate)
- Circuit Test B - Checking Vehicle Battery
- Circuit Test C - Reference Voltage
- Circuit Test DA - Temperature Sensor Test (IAT & ECT)
- Circuit Test Db - EGR Temperature (EGRT) Sensor
- Circuit Test Dc - Mass Airflow (MAF) Sensor
- Circuit Test Dd - EGR Position (EGRP) Sensor, EGR Vacuum (EGRV) Solenoid & EGR Atmospheric (EGRA) Solenoid
- Circuit Test De - Flex Fuel (Ff) Sensor
- Circuit Test DF - Map/Barometric Pressure (BARO) Sensor
- Circuit Test Dg - Knock Sensor (KS)
- Circuit Test DH - Throttle Position (TP) Sensor
- Circuit Test DL - Pressure Feedback EGR (PFE) Valve, Delta
- 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) Circuit
- Circuit Test FD - Brake On-Off (Boo) Switch
- Circuit Test FE - Electrical Load Inputs
- Circuit Test Ff - Power Steering Pressure (PSP) Switch
- Circuit Test G - MAF/TPS Fuel Injector Pulse Width Test
- Circuit Test H - Fuel Control
- Circuit Test Ha - Adaptive Fuel Strategy
- Circuit Test HB - Flex Fuel Control
- Circuit Test J - Fuel Pump Circuit (Relay & Inertia Switch)
- Circuit Test KA - EGR Vacuum Regulator (EVR) Solenoid
- Circuit Test Kb - Canister Purge (CANP) Valve
- CKT Test Kc - Secondary Air Injection Solenoids (AIRB/AIRD)
- Circuit Test KD - Canister Purge (CANP)
- Circuit Test KE - Idle Air Control (IAC) Solenoid
- 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 Reg CNTRL (FPRC) Solenoid
- Circuit Test KP - Octane Adjust
- Circuit Test Kt - Intake Manifold Runner CNTRL (IMRC) System
- Circuit Test M - Dynamic Response Test
- Circuit Test Ml - Self-Test Output (STO) Or Malfunction Indicator LT (Mil)
- Circuit Test NA - Distributor Ignition System Ignition Diagnostic Monitor (IDM)
- Circuit Test NB - Ignition Diagnostic Monitor (IDM) DISTRIBUTORLESS Ignition System (Low Data Rate)
- Circuit Test NC - Ignition Diagnostic Monitor (IDM) DISTRIBUTORLESS Ignition System (High Data Rate)
- CKT Test Pa - Spark Timing Check (Distributor IGN Systems)
- Circuit Test PB - Spark Timing Check DISTRIBUTORLESS IGN System (Low Data Rate)
- Circuit Test Pc - Spark Timing Check DISTRIBUTORLESS Ignition System (High Data Rate)
- Circuit Test QA - No Codes/Codes Not Listed
- Circuit Test QB - Diagnostic Trouble Code 512
- Circuit Test QC - Output State Check Not Functioning
- Circuit Test S - System Check
- Circuit Test Ta - Clutch Pedal Position (CCP) Switch/Park/Neutral Position (PNP) Switch
- Circuit Test Tb - Transmission CNTRL SW (TCS), Transmission CNTRL SW Module (TCSM) & Trans CNTRL Indicator Light (TCIL)
- Circuit Test TC - Transmission Solenoids
- Circuit Test TD - Manual Lever Position (MLP) Sensor
- Circuit Test Te - Transmission Fluid Temperature (TFT) Sensor
- Circuit Test TF - Transmission Speed Sensor
- CKT Test TG - Elect Trans Continuous Mem Diag Trouble Codes
- Circuit Test X - Constant Control Relay Module (CCRM)
- Circuit Test XB - Variable Control Relay Module (VCRM)
- Summary
- Wiring Diagrams
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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.