Engine Controls - Diagnostic Methods (Except Diesel & Hybrid): Diagnosis Mercury Sable V

Diagnostic Tools

Below is an equipment list with corresponding part numbers

REQUIRED EQUIPMENT

1. Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool with functionality described under Scan Tool Setup and Functionality.
2. Rotunda Smoke Machine, Fuel Evaporative Emission System Tester 218-00001 (522) or equivalent.

RECOMMENDED EQUIPMENT

1. Rotunda Vacuum/Pressure Tester 164-R0253 or equivalent. Range 0-101.3 kPa (0-30 in-Hg.) Resolution 3.4 kPa (1 in-Hg.)
2. Rotunda Vacuum Tester 014-R1054 or equivalent. Range 0-101.3 kPa (0-30 in-Hg.)
3. Rotunda 73III Automotive Meter 105-R0057 or equivalent. Input impedance 10 Megaohm minimum.
4. Spark Tester D81P-6666-A (303-D037) or equivalent.
5. Non-powered test lamp.

OPTIONAL EQUIPMENT

1. Rotunda Fuel (Gasoline) pressure test kit 134-R0087 or equivalent. (Use tool manufacturer's instructions.)

Scan Tool Setup and Functionality

Connect the scan tool to the data link connector (DLC) for communication with the vehicle.

The DLC is located in the driver side compartment under the steering column. It is attached to the instrument panel and accessible from the driver seat.

The DLC is rectangular in design and capable of accommodating up to 16 terminals. The connector has keying features to allow easy connection.

The required scan tool functions are described below

1. monitor, record, and playback of parameter identification (PIDs)
2. freeze frame PID data
3. diagnostic test modes; self-test, clear diagnostic trouble codes (DTCs)
4. output test mode
5. resetting keep alive memory (KAM)
6. diagnostic monitoring test results (mode 6) for on board diagnostic (OBD) on board monitors
7. on-board system readiness (OBD monitor completion status)

Some of these functions are described. Refer to the scan tool manufacturer's instruction article for specific information on scan tool setup and operation.

Quick Test

The quick test is divided into 3 specialized tests

1. Key On Engine Off (KOEO) On-Demand Self-Test
2. Key On Engine Running (KOER) On-Demand Self-Test
3. Continuous Memory Self-Test

The quick test checks the integrity and function of the electronic engine control (EEC) system and outputs the test results when requested by the scan tool. The quick test also provides a quick check of the powertrain control system, and is usually carried out at the start of each diagnostic procedure with all accessories off. The quick test is also carried out at the end of most pinpoint tests for verification of the repair and to make sure no other concerns are incurred while repairing a previous concern. A system pass is displayed when no diagnostic trouble codes (DTCs) are output and a scan tool communication error does not exist. System pass means that hardware monitored by the powertrain control module (PCM) is functioning within the normal operating limits. Only a system pass, a DTC, or an incomplete on board diagnostic (OBD) drive cycle (P1000) is displayed.

For applications that use a stand-alone transmission control module (TCM) the PCM does not output TCM DTCs. For TCM self-test and diagnostics, refer to the AUTOMATIC TRANSAXLE/TRANSMISSION - 4R70E/4R75E -- E-SERIES .

Key On Engine Off (KOEO) On-Demand Self-Test

The KOEO on-demand self-test is a functional test of the PCM carried out on-demand with the key on and the engine off. This test carries out checks on certain sensor and actuator circuits. A concern must be present at the time of testing for the KOEO self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.

Key On Engine Running (KOER) On-Demand Self-Test

The KOER on-demand self-test is a functional test of the PCM carried out on-demand with the key on, the engine running and the vehicle stopped. A check of certain inputs and outputs is made during operating conditions and at a normal operating temperature. The brake pedal position, transmission control, and the power steering tests are part of the KOER on-demand self-test and must be carried out during this operation if applicable. These are described below. A concern must be present at the time of testing for the KOER on-demand self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.

Brake Pedal Position (BPP) Test

The BPP test checks the ability of the EEC system to detect a change of state in the BPP switch. The brake pedal is briefly applied and released on all vehicles equipped with a BPP input. This is done during a KOER on-demand self-test.

Power Steering Pressure (PSP) Test

The PSP test checks the ability of the EEC system to detect a change in the power steering system fluid pressure. The steering wheel is briefly turned at least 1/4 of a revolution on vehicles equipped with a PSP switch or sensor. This is done during a KOER on-demand self-test.

Transmission Control Switch (TCS) Test

The TCS test checks the ability of the EEC system to detect a change of state in the TCS. The switch is briefly cycled on all vehicles equipped with a TCS input. This is done during a KOER on-demand self-test.

Continuous Memory Self-Test

The continuous memory self-test is a functional test of the PCM carried out under any condition (engine running or off) with the key on. Unlike the KOEO and KOER self-tests, which can only be activated on-demand, the continuous self-test is always active. A concern does not need to be present when accessing continuous memory self-test DTCs, making the test valuable when diagnosing intermittent concerns. The vehicle may need to be driven or the on board diagnostic (OBD) drive cycle completed to allow the PCM to detect a concern. Refer to ON BOARD DIAGNOSTIC (OBD) DRIVE CYCLE for more information. When a concern is stored in memory, a DTC is output on the data link when requested by the scan tool.

There are two types of continuous DTCs. The first type is an emission-related code which illuminates the malfunction indicator lamp (MIL) in the instrument cluster. The second is a non-emission related, non-MIL code which does not illuminate the cluster indicator.

For emission-related MIL codes, the PCM stores the DTC in continuous memory when a concern is detected for the first time. At this point the DTC does not illuminate the MIL and is now considered a pending code. The purpose of pending codes is to assist in repair verification by reporting a pending DTC after one drive cycle. If the same concern is detected after the next ignition start-run cycle, the emission-related MIL code illuminates the MIL. The MIL remains on even if the concern is intermittent. The MIL is extinguished if the concern is not present through 3 consecutive drive cycles or if the concern is fixed and the DTCs are cleared. Also, an emission-related pending MIL and any non-emission related, non-MIL DTCs are erased after approximately 40 vehicle warm-up cycles or if the DTCs are cleared.

Any scan tool that meets OBD requirements can access the continuous memory to retrieve emission-related MIL DTCs. However, not all scan tools access pending and non-emission related, non-MIL DTCs in the same way.

During most diagnostic procedures in this article, it is required that all DTCs be retrieved and cleared. Consult the instruction article from the tool manufacturer for specific instructions.

Diagnostic Monitoring Test Results - Mode 6

Mode 6 allows access to the results of on board diagnostic (OBD) monitor diagnostic test results. The test values are stored at the time of the particular monitor completion. Refer to mode 6 on the scan tool for test information.

Intermittent Diagnostic Techniques

Intermittent diagnostic techniques help find and isolate the root cause of intermittent concerns associated with the electronic engine control (EEC) system. The information is organized to help find the concern and carry out the repair. The process of finding and isolating an intermittent concern starts with recreating a fault symptom, accumulating powertrain control module (PCM) data, and comparing that data to typical values, then analyzing the results. Refer to the scan tool manufacturer's instruction article for the functions described below.

Before proceeding, be sure that

1. Customary mechanical system tests and inspections do not reveal a concern. NOTE: Mechanical component conditions can make a PCM system react abnormally.
2. Technical Service Bulletins (TSBs) and On-line Automotive Service Information System (OASIS) messages, if available, are reviewed.
3. Quick Test and associated diagnostic subroutines have been completed without finding a concern, and the symptom is still present.

Adaptive Fuel Diagnostic Trouble Code (DTC) Diagnostic Techniques

The Adaptive Fuel DTC Diagnostic Techniques help isolate the root cause of the adaptive fuel concern. Before proceeding, attempt to verify if any driveability concerns are present. These diagnostic aids are meant as a supplement to the pinpoint test steps. For a description of fuel trim, refer to POWERTRAIN CONTROL SOFTWARE , Fuel Trim.

Obtain Freeze Frame Data

Freeze frame data is helpful in duplicating and diagnosing adaptive fuel concerns. The data (a snapshot of certain parameter identification (PID) values recorded at the time the DTC is stored in Continuous Memory) is helpful to determine how the vehicle was being driven when the concern occurred, and is especially useful on intermittent concerns. Freeze frame data, in many cases, helps to isolate possible areas of concern as well as rule out others. Refer to FREEZE FRAME DATA for a more detailed description of this data.

Using the LONGFT1 and LONGFT2 (Dual Bank Engines) PIDs

The LONGFT1/2 PIDs are useful for diagnosing fuel trim concerns. A negative PID value indicates that fuel is being reduced to compensate for a rich condition. A positive PID value indicates that fuel is being increased to compensate for a lean condition. It is important to know that there is a separate LONGFT value that is used for each RPM/load point of engine operation. When viewing the LONGFT1/2 PIDs, the values may change a great deal as the engine is operating at different RPM and load points. This is because the fuel system may have learned corrections for fuel delivery concerns that can change as a function of engine RPM and load. The LONGFT1/2 PIDs display the fuel trim currently being used at that RPM and load point. Observing the changes in LONGFT1/2 can help when diagnosing fuel system concerns. For example

1. A contaminated mass air flow (MAF) sensor results in matching LONGFT1/2 correction values that are negative at idle (reducing fuel), but positive (adding fuel) at higher RPM and loads.
2. LONGFT1 values that differ greatly from LONGFT2 values rule out concerns that are common for both banks (for example, fuel pressure concerns, MAF sensor, etc. can be ruled out).
3. Vacuum leaks result in large rich corrections (positive LONGFT1/2 value) at idle, but little or no correction at higher RPM and loads.
4. A plugged fuel filter results in no correction at idle, but large rich corrections (positive LONGFT1/2 value) at high RPM and load.

Resetting Long Term Fuel Trims

Long term fuel trim corrections are reset by resetting the keep alive memory (KAM). Refer to RESETTING THE KEEP ALIVE MEMORY (KAM) . After making a fuel system repair, the KAM must be reset. For example, if dirty/plugged injectors cause the engine to run lean and generate rich long term corrections, installing new injectors and not resetting the KAM causes the engine to run very rich. The rich correction eventually leans out during closed loop operation, but the vehicle may have poor driveability and high CO emissions while it is learning.

DTCs P0171/P0174 System Too Lean Diagnostic Aids

Note. If the system is lean at certain conditions, then the LONGFT PID would be a positive value at those conditions, indicating that increased fuel is needed.

The ability to identify the type of lean condition causing the concern is crucial to a correct diagnosis.

Air Measurement System

With this condition, the engine runs rich or lean of stoichiometric (14.7:1 air/fuel ratio) if the powertrain control module (PCM) is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs lean at higher RPM because the PCM delivers fuel for less air than is actually entering the engine. Examples

1. The MAF sensor measurement is inaccurate due to a corroded connector, contaminated or dirty connector. A contaminated MAF sensor typically results in a rich system at low airflow (PCM reduces fuel) and a lean system at high airflow (PCM increases fuel).

Vacuum Leaks/Unmetered Air

With this condition, the engine runs lean of stoichiometric (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition is caused by unmetered air entering the engine, or due to a MAF concern. In this situation, the volume of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. Vacuum leaks are normally most apparent when high manifold vacuum is present (for example, during idle or light throttle). If freeze frame data indicates that the concern occurred at idle, a check for vacuum leaks/unmetered air is the best starting point. Examples

1. loose, leaking, or disconnected vacuum lines
2. intake manifold gaskets, or O-rings
3. throttle body gaskets
4. brake booster
5. air inlet tube
6. stuck/frozen/aftermarket positive crankcase valve (PCV)
7. unseated engine oil dipstick.

Insufficient Fueling

With this condition, the engine runs lean of stoichiometric (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition is caused by a fuel delivery system concern that restricts or limits the amount of fuel being delivered to the engine. This condition is normally apparent as the engine is under a heavy load and at high RPM, when a higher volume of fuel is required. If the freeze frame data indicates that the concern occurs under a heavy load and at higher RPM, a check of the fuel delivery system (checking fuel pressure with engine under a load) is the best starting point. Examples

1. low fuel pressure (fuel pump, fuel filter, fuel leaks, restricted fuel supply lines)
2. fuel injector concerns

Exhaust System Leaks

In this type of condition, the engine runs rich of stoichiometric (14.7:1 air/fuel ratio) because the fuel control system is adding fuel to compensate for a perceived (not actual) lean condition. This condition is caused by oxygen (air) entering the exhaust system from an external source. The HO2S reacts to this exhaust leak by increasing fuel delivery. This condition causes the exhaust gas mixture from the cylinder to be rich. Examples

1. exhaust system leaks upstream or near the HO2S
2. cracked/leaking HO2S boss
3. inoperative secondary air injection system

DTCs P0172/P0175 System Too Rich Diagnostic Aids

Note. If the system is rich at certain conditions, then the LONGFT PID would be a negative value at that airflow, indicating that decreased fuel is needed.

System rich concerns are caused by fuel system concerns, although the MAF sensor and base engine (for example, engine oil contaminated with fuel) should also be checked.

Air Measurement System

With this condition, the engine runs rich or lean of stoichiometric (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs rich at idle because the PCM delivers fuel for more air than is actually entering the engine. Examples

1. MAF sensor measurement inaccurate due to a corroded connector, contamination/dirt. A contaminated MAF sensor typically results in a rich system at low airflow (PCM reduces fuel) and a lean system at high airflow (PCM increases fuel).

Fuel System

With this condition, the engine runs rich of stoichiometric (14.7:1 air/fuel ratio), if the PCM is not able to compensate enough to correct for the condition. This situation causes a fuel delivery system that is delivering excessive fuel to the engine.

Examples

1. fuel pressure regulator causes excessive fuel pressure (system rich at all airflow), fuel pressure is intermittent, going to pump deadhead pressure, then returning to normal after the engine is turned off and restarted.
2. fuel pulse dampener diaphragm ruptured (fuel leaking into the intake manifold, system rich at lower airflow).
3. fuel injector leaks (injector delivers extra fuel).
4. EVAP canister purge valve leak (if the canister is full of vapors, introduces extra fuel).
5. fuel rail pressure (FRP) sensor (electronic returnless fuel systems) concern causes the sensor to indicate a lower pressure than actual. The PCM commands a higher duty cycle to the fuel pump driver module (FPDM), causing high fuel pressure (system rich at all airflow).

Air Inlet System

A restriction within any of the following components may be significant enough to affect the ability of the PCM adaptive fuel control.

1. air inlet tube
2. air cleaner element
3. air cleaner assembly
4. resonators
5. clean air tube

Base Engine

Engine oil contaminated with fuel can contribute to a rich-running engine.