Diagnostic equipment
1. To check the condition of the injection system elements and reduce exhaust toxicity, you must use a digital multimeter (see illustration). The new digital instrument should be preferred over the previously developed analog multimeter for the following reasons. An analog multimeter does not record hundredths and thousandths of Volts, Amperes and Ohms. Measurement accuracy is especially important when testing electronic circuits, which are often at low voltage. Another factor indicating the preference of a digital multimeter is the high resistance of its internal circuit. A digital device has internal circuitry with extremely high resistance (10000000 Ohm). Since the voltmeter is connected in parallel to the circuit under test, it is very important that no voltage is applied to the parallel circuit into which the voltmeter directly connects. When measuring high voltage circuits (9 - 12 V) Loss of voltage in the parallel circuit does not significantly affect the measurement results. In contrast, when diagnosing low voltage circuits, such as the circuit containing the oxygen level sensor, the loss may be commensurate with the total voltage of the circuit. There are some exceptional cases where the use of an analog instrument is necessary to test some sensors.
2.1. Digital multimeters can be used to test all types of circuits; Due to the high resistance of internal circuits, these devices are more accurate than analog multimeters. which is essential when measuring on low voltage circuits connected to the system processor
2. Portable scanners are the most effective and versatile devices for diagnosing engine management systems of cars of recent years (see illustration). Before starting diagnostics, make sure that the existing scanner matches the manufacturer, modification and year of manufacture of the vehicle being diagnosed. It is often possible to purchase special cartridges for the scanner, with which you can diagnose cars of specific brands (FORD, GMC, CHRYSLER and t. d.). Some brands are classified according to where they are assembled (Asia. Europe, USA, etc.).
2.2. Actron OBD-II, Actron Scantool and AutoXray XP240 scanners are powerful diagnostic equipment. Such devices are equipped with diagnostic software, so they are able to display almost any information related to the engine management system
3. When working with the OBD-II diagnostic system, you must use a special scanner. Such scanners are developed and produced by several manufacturers. Before purchasing a scanner, obtain additional information from the store regarding the range of diagnostic scanners and their prices.
General description of the OBD system
4. All described vehicles are equipped with a second generation OBD-II on-board diagnostic system. The system consists of an on-board computer (RSM), information sensors and drive devices.
5. The PCM unit receives impulses from various sensors and other electronic devices (switches, relays, etc.). After processing the received information from the PCM, control signals are received for various drive relays, solenoid valves and other devices (for example, fuel injectors). The PCM is specially tuned to optimize fuel economy, engine performance and emissions.
6. Since the engine control system has a warranty that expires if system elements are damaged by independent influence, you should not diagnose or replace the PCM at home until the warranty period has expired. If the warranty period has not expired, if the system or PCM malfunctions, you should contact the original station.
System sensors
7. Accelerator pedal position sensor (ARR) located on the accelerator pedal, and consists of two separate switches housed in a single housing. Thus, two separate pulses are generated: one in the low voltage circuit, and the other in the 5 Volt circuit. The voltage of the first switch increases as the accelerator pedal is depressed, and the voltage of the second switch decreases. The APP sensor, together with other information sensors, ensures the operation of the automatic throttle drive system.
8. Camshaft position sensor (construction and installation work) transmits a signal to the PCM that determines the position of the camshaft. Based on the pulses of this sensor, as well as the crankshaft position sensor, the fuel injection phases are synchronized in the PCM.
9. Crankshaft position sensor (TFR) transmits a signal to the control unit that determines the crankshaft position corresponding to TDC of the first piston during each engine operating cycle. Based on the received pulses, the PCM block controls the ignition phases and synchronizes the fuel injection phases.
10. Coolant temperature sensor (EATING) transmits a signal to the PCM, on the basis of which the coolant temperature is determined. The sensor signals are taken into account when determining the optimal air-fuel mixture ratio, as well as when calculating the ignition timing.
11. Supply air temperature sensor (IAT) used to determine the temperature of the air entering the intake manifold. The sensor pulses are the initial ones when determining the duration of injector opening in the PCM.
12. Knock sensor (KS) contains a piezoelectric element that emits pulses depending on the vibration of the cylinder block. The signals determine the presence of engine detonation. When the corresponding sensor signals are received by the PCM, the ignition angle is reduced, thereby preventing detonation.
13. Manifold absolute pressure sensor (IDA) used to determine the pressure in the intake manifold, as well as external atmospheric pressure. Based on incoming signals, the RSM determines the load on the engine, in accordance with changes in which the air-fuel mixture ratio is adjusted.
14. Incoming air quantity sensor (MAF) designed to determine the mass of air passing through the sensor housing and entering the engine. The sensor signals are processed in the PCM, where the amount of fuel required to form the optimal air-fuel mixture is determined.
15. Oxygen sensor (Og) produces signals that vary depending on the oxygen content in the exhaust. Based on the sensor signals in the PCM, the air-fuel mixture ratio is determined. If necessary, the mixture is depleted or enriched.
16. Throttle position sensor (TPS) registers movement and determines the position of the throttle valve. The corresponding signal is transmitted to the PCM, on the basis of which the closed, normal or fully open position of the throttle unit is determined. These data, together with the signals from other sensors, determine the period of opening of the injector valves, and also serve as the basis for automatic adjustment of the ignition timing. It should be noted that on the vehicles described, the sensor is integrated into the throttle unit. If necessary, the entire unit is replaced.
17. Vehicle speed sensor (VSS) transmits a signal to the PCM that determines the speed of the vehicle.
18. Other input signals of the electronic unit enter the PCM from various switches and electrical circuits, the state of which determines the operating mode of the vehicle. These pulses come from the following switches and electrical circuits.
- A) Air conditioning system
- b) Battery power circuit
- With) Brake light sensor
- d) Speed control system
- e) EGP valve position sensor
- f) Engine oil pressure and level sensor
- g) Evaporative emission system
- h) Fuel level and pressure sensor in the gas tank
- i) Egnition lock
- j) Sensor for selector lever in Park/Neutral position (PNP)
- k) Sensor signal circuits and ground loops
- l) Transmission switches
Drive devices of the system
19. The air conditioning clutch relay provides control of the compressor clutch from the electronic PCM.
20. The camshaft timing adjustment system receives impulses from the PCM to the solenoid valve of the actuator, thereby adjusting the position of the camshaft cams to optimize engine performance.
21. Indicator «Service Engine Soon» turns on from the PCM when a problem occurs in the electronic engine control system.
22. The speed control device is controlled by the PCM to ensure the system operates «Cruise control».
23. The engine cooling fan relay is used to electronically control the fan from the PCM depending on the pulses of the coolant temperature sensor.
24. The EVAP canister purge and vent valve solenoids are controlled by the PCM to purge the canister and direct fuel vapor from it into the intake manifold for combustion in the engine chambers.
25. Fuel injectors are opened by the PCM in a separate order in accordance with the ignition sequence. The electronic unit also monitors the open time of the injector (pulse width). This value (measured in milliseconds) determines the amount of fuel supplied. A detailed description of the fuel supply system, as well as the operating principle and procedure for replacing injectors, is given in Chapter 4.
26. The fuel pump relay is turned on from the PCM when the ignition key is turned to the Start or Run position. When the ignition switch is closed, the relay is activated and primary fuel pressure is created in the system. Chapter 4 describes the procedures for testing and replacing the fuel pump.
27. Idle valve (IAC) designed to regulate the air flow that bypasses the throttle block when it is completely closed or in the idle position. The valve receives signals from the PCM. When the engine is under additional load (for example, low speed maneuvering, air conditioning operation, etc.) The idle speed may drop until the engine stops. To prevent this situation, additional air flows through the valve, which allows you to maintain the engine speed required to overcome the load.
28. The ignition coils/ignition unit are controlled by the PCM, which is carried out depending on the operating conditions of the engine. Chapter 5 provides more information on ignition coils and the ignition unit.
Reading fault codes from the electronic memory of the microprocessor
Note: to obtain fault codes from the memory of the PCM microprocessor, it is necessary to use a special scanner. If you do not have the required diagnostic device, take the vehicle to a dealership.
29. If the PCM registers a malfunction in the emission control system, as well as in its individual elements and electrical circuits, the SERVICE ENGINE SOON indicator on the instrument panel turns on, which is sometimes called a malfunction indicator (MIL). The indicator will work until the malfunction is eliminated and the PCM code is deleted from the electronic memory, or until this malfunction is registered over several driving cycles.
30. To obtain codes from the PCM memory, it is necessary to use a special scanner. Connect the scanner, which has an interface combined with the OBD-II system, to the vehicle’s diagnostic connector (see illustration). The use of this equipment makes it possible to determine the root causes of engine malfunctions. The scanner also has a function for freezing the basic parameters of the corresponding sensors and drive devices when a problem occurs in the engine control systems or reduces exhaust emissions. The parameters recorded at the time the fault code was recorded are stored in memory. The presence of this function allows you to examine circuits and evaluate their parameters when diagnosing faults that are intermittent in nature. If a malfunction of an intermittent nature occurs and there is no diagnostic scanner, take the car to a company station for examination.
2.30. Typically, the diagnostic connector is located under the instrument panel
Removing fault codes from the electronic memory of the microprocessor
31. After determining the cause of the malfunction, repair or replace the failed elements and clean the PCM electronic memory. It is preferable to remove codes from memory using a scanner, but this can also be done by disconnecting the battery from the electronic power supply for at least 30 seconds. You can turn off the power by removing the PCM fuse by disconnecting the PCM power circuit connector located near the positive battery terminal (if the presence of a connector is provided for by the design), as well as disconnecting the negative cable from the battery. After installing new electronic elements of the emission reduction system, before starting the engine, it is necessary to clear the electronic memory of the microprocessor from fault codes. The PCM memory stores the operating parameters of each sensor. If the new sensor is put into operation before the parameters of the old sensor are deleted, a fault code may be registered in the PCM.
Decoding diagnostic codes
32. The table below provides a breakdown of the codes that a car mechanic can receive when performing the procedures independently. When diagnosing in a company center, using special equipment and software, significantly more diagnostic codes can be obtained. Not all codes apply to the specific model of the series being described. The registration of a fault code is not always accompanied by the SERVICE ENGINE SOON indicator turning on. To obtain fault codes on all models, you must use a diagnostic scanner.
Code | Probable Cause |
R 0013 | Malfunctions in the electrical circuit of the camshaft phase adjustment device |
P0014 | Camshaft phase period failure |
R 0105 | The voltage in the MAP sensor circuit is outside the set limit |
R 0107 | Weak MAP sensor circuit input (IDA) |
P0108 | MAP sensor circuit high input (IDA) |
P0112 | IAT Sensor Circuit Input Weak |
R 0113 | Extremely high IAT sensor circuit input |
R 0117 | Weak ECT sensor circuit input |
R 0118 | Extremely high ECT sensor circuit input |
R 0122 | Weak TP sensor circuit input signal |
R 0123 | Extremely high TP sensor circuit input |
R 0125 | Coolant temperature too low to activate fuel system feedback loop |
R 0128 | Ambient temperature too low (EATING) |
P0130 | Inconsistency of signals and operating characteristics of the oxygen sensor circuit |
R 0131 | Weak signal in the oxygen sensor circuit (top sensor, left row) |
R 0132 | Extremely high signal in the oxygen sensor circuit (top sensor, left row) |
R 0133 | Slow oxygen sensor circuit feedback (top sensor, left row) |
R 0134 | No oxygen sensor circuit activity (top sensor, left row) |
R 0135 | Problems in the oxygen sensor heating element circuit (top sensor, left row) |
R 0137 | Weak signal in the oxygen sensor circuit (lower sensor, left row) |
R 0138 | Extremely high signal in the oxygen sensor circuit (lower sensor, left row) |
R 0140 | No oxygen sensor circuit activity (lower sensor, left row) |
R 0141 | Problems in the oxygen sensor heating element circuit (lower sensor, left row) |
R 0171 | Lean air-fuel mixture, left row |
R 0172 | Enrichment of the air-fuel mixture, left lane |
R 0175 | Enrichment of the air-fuel mixture, right lane |
R 0201 - R 0206 | Problems in the injector control circuit of one of the cylinders |
R 0300 | Misfires |
R 0301- R 0306 | Misfire in a specific cylinder |
R 0326 | Malfunction in the knock sensor diagnostic circuit |
R 0327 | Knock Sensor Circuit Low Output (front knock sensor) |
P0332 | Knock Sensor Circuit Low Output (rear knock sensor) |
P0335 | Problems in the crankshaft position sensor circuit |
R 0336 | Incorrect value or characteristics of the crankshaft position sensor signal |
R 0340 | Malfunctions in the camshaft position sensor circuit |
R 0341 | Incorrect value or characteristics of the camshaft position sensor signal |
R 0420 | Reduced efficiency of the catalytic reduction system, left lane |
R 0440 | Problems with the fuel vapor recovery system |
R 0442 | Minor gas leak from the EVAP system |
R 0446 | Incorrect value or signal characteristics in the EVAP system vent valve circuit |
R 0449 | Problems in the EVAP system vent valve control circuit |
R 0452 | EVAP Pressure Sensor Circuit Low Input |
R 0453 | EVAP Pressure Sensor Circuit Input Excessively High |
R 0480 | Problems in the cooling fan relay control circuit |
R 0483 | Error when determining cooling fan speed |
R 0493 | Error when determining cooling fan speed |
R 0495 | Overestimation of the required cooling system fan speed |
R 0502 | Vehicle Speed Sensor Circuit Low Input |
R 0503 | Intermittent failure in vehicle speed sensor circuit |
R 0506 | Malfunction of the IAC sensor, as a result of which the idle speed decreases |
R 0507 | IAC sensor malfunction resulting in high idle speed |
R 0526 | Loss of the signal that determines the speed of the cooling fan |
R 0562 | Low system voltage |
R 0563 | System high voltage |
P0601 | An error has been detected in the electronic memory of the PCM |
R 0602 | An error has been detected in the PCM program |
R 0603 | An error is detected when rebooting the electronic memory of the PCM |
R 0604 | A random error was detected in the PCM RAM (RAM) error |
P0605 | In the PCM storage device (ROM) error detected |
P0621 | Malfunction of the circuit connected to the generator terminal L |
R 0622 | Malfunction of the circuit connected to terminal F of the generator |
R 0705 | Malfunction in the sensor circuit of the selector position sensor in the Park/Neutral position |
R 0711 | Inconsistency with the signal characteristics in the transmission oil temperature sensor circuit |
R 0712 | Transmission Oil Temperature Sensor Circuit Low Input |
R 0713 | Transmission Oil Temperature Sensor Circuit High Input |
R 0719 | Torque Converter Clutch Brake Switch Circuit Low Signal |
R 0724 | Torque Converter Clutch Brake Switch Circuit High Signal |
R 0740 | Torque converter clutch solenoid valve is not controlled via circuit |
R 0741 | Torque converter jammed in disengaged position |
R 0742 | Torque converter jammed in on position |
R 0748 | Malfunction in the pressure control valve circuit |
R 0751 | Non-compliance with the signal characteristics of the solenoid valve circuit for switching from 1st to 2nd gear |
R 0753 | Malfunction in the solenoid valve circuit for switching from 1st to 2nd gear |
R 0756 | Non-compliance with the signal characteristics of the solenoid valve circuit for switching from 2 to 3 gears |
R 0758 | Malfunction in the solenoid valve circuit for shifting from 2nd to 3rd gear |
R 0785 | Malfunction in the solenoid valve circuit for shifting from 2nd to 3rd gear |
R 1120 | Throttle Position Sensor 1 Circuit Low Voltage |
R 1133 | Poor oxygen sensor switching (upstream oxygen sensor) |
P1134 | Violation of the temporary phases of operation of the oxygen sensor (upstream oxygen sensor) |
P1137 | Low voltage in the oxygen sensor circuit (downstream oxygen sensor) |
P1138 | Oxygen sensor circuit high voltage (downstream oxygen sensor) |
P1171 | During acceleration, the air-fuel mixture becomes leaner |
R 1220 | Throttle Position Sensor Signal Characteristics Inconsistency |
R 1221 | Mismatch between two throttle position sensors |
R 1258 | Enabling the engine overheat protection mode |
R 1271 | Excessive voltage difference between accelerator pedal position sensors 1 and 2 (ARR) |
P1275 | High or low voltage in the accelerator pedal position sensor circuit |
R 1280 | Mismatch between two sensors 1 and 2 of the accelerator pedal position |
R 1336 | Crankshaft position sensor modes are not memorized |
R 1345 | Crankshaft Position/Camshaft Position Sensor Correlation |
R 1380 | Error when detecting uneven road surface in the electronic brake system unit |
R 1381 | Serial data is not received from the electronic brake system unit |
R 1441 | The fuel vapor recovery system vents without purging |
R 1481 | Loss of the signal that determines the speed of the cooling fan |
R 1482 | Incorrect voltage in the cooling fan clutch circuit |
R 1484 | Error when determining cooling fan speed |
R 1512 | Intended or past error in determining throttle position |
R 1514 | Air meter (MAF), the air flow intensity differs from the calculated value |
R 1515 | Throttle position sensor (TPS), difference between real and defined throttle position |
R 1516 | Throttle Position Sensor Signal Characteristics Inconsistency (TPS) |
P1621 | Non-compliance with the standard characteristics of the parameters of the electronic memory of the PCM |
R 1630 | Problems with the anti-theft alarm system controller (time exceeded in password entry mode) |
R 1631 | Entering the wrong anti-theft alarm system password |
R 1633 | No voltage at ignition switch position 0, and presence at position 1 |
R 1635 | 5 Volt circuit |
R 1637 | Problems in the circuit connected to the generator terminal L |
R 1638 | Malfunctions in the electromagnetic cycle of the generator |
R 1639 | 5 Volt circuit |
R 1682 | Voltage at ignition switch position 1 is less than 10 Volts |
R 1810 | Malfunction of the oil pressure sensor in the gearbox |
R 1860 | Problems in the solenoid valve circuit of the torque converter clutch pulse width changer |
R 1870 | Transmission slipping |