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 MANUALSMERCURY1991COUGAR LS, 3.8 4REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 3.8L
1991 Mercury Cougar LS, 3.8 4
Engine Controls - Tests W/Codes - 3.8L
1991 Mercury Cougar LS, 3.8 4SECTION Engine Controls - Tests W/Codes - 3.8L
- Introduction
- Self-Diagnostic System
- Service Codes
- Retrieving Codes
- Clearing Codes
- Reading Codes
- Quick Test
- Additional System Functions
- KOEO Code/Test Menu - 3.8L
- KOER Code/Test Menu - 3.8L
- Continuous Code/Test Menu - 3.8L
- Service Code Definitions
- Test Pin Identification
- How To Use Circuit Tests
- Test A - No Start (TFI & Dis Ignition Systems)
- Test B - Checking Vehicle Battery
- Test C - Reference Voltage
- Test DA - Temperature Sensor Test (Act & ECT)
- Test Dc - Mass Airflow Sensor (MAF)
- Test DF - Map/BP Sensor (3.8L SPFI-Ma SC Only)
- Test Dg - Knock Sensor (KS) (3.8L SPFI-Ma SC Only)
- Test DH - Throttle Position Sensor (TPS)
- Test DL - PFE Valve, DPFE Sensor & EVR Solenoid
- Test DN - EVP Sensor & EVR Solenoid
- Test DP - Vehicle Speed Sensor (VSS)
- Test Dr - Cylinder Identification (CID) Sensor
- Test FD - Brake On-Off (Boo) Switch
- Test Ff - Power Steering Pressure Switch (PSPS)
- Test G - In-Range MAF/TPS Fuel Injector Pulse Width Test
- Test H - Fuel Control
- Test Ha - Adaptive Fuel
- Test J - Fuel Pump Circuit (Relay & Inertia Switch)
- Test KD - Canister Purge (CANP)
- Test KE - Idle Speed Control (Air By-Pass)
- Test KF - EDF & HEDF
- Test Kl - Shift Indicator Light (SIL)
- Test Km - WAC & A/C Demand Switches
- Test KP - Octane Adjust
- Test M - Dynamic Response Test
- Test Ml - STO Or Mil Lights
- Test NA - TFI Ignition Ignition Diagnostic Monitor (IDM)
- Test NB - Dis Ignition Ignition Diagnostic Monitor (IDM)
- Test Pa - Spark Timing Check (TFI Vehicles)
- Test PB - Spark Timing Check (Dis Vehicles)
- Test QA - No Codes/Codes Not Listed
- Test QB - Code 15, 511 Or 512 KOEO Or Continuous Memory Code
- Test QC - Output State Check Not Functioning
- Test S - System Check
- Test T - AXODE Transaxle
- Test Ta - Neutral Drive Input
- 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.