Information about diagnostic devices
The proper functioning of injection system components and exhaust gas toxicity reduction systems is checked using a universal digital meter (multimeter). Using a digital meter is preferable for several reasons. Firstly, it is quite difficult to measure the value of an analog meter (sometimes it's impossible), determine the result of the reading with an accuracy of up to hundredths and thousandths, while when examining circuits that include electronic components, such accuracy becomes especially important. The second, no less important, reason is the fact that the internal circuit of the digital multimeter has a fairly high impedance (the internal resistance of the device is 10 million ohms). Since the voltmeter is connected to the circuit being tested in parallel, the accuracy of the measurement is higher, the smaller the parasitic current that passes through the device itself. This problem is not significant when measuring relatively high voltage values (9÷12 V), but it becomes vital when diagnosing elements that produce low-voltage signals, such as, for example, an oxygen sensor, where we are talking about measuring fractions of a volt.
The most convenient device for diagnosing engine management systems of modern car models are hand-held scanner-type readers (see illustration below). First generation scanners are used to read OBD-I system trouble codes. Before use, the reader should be checked for compliance with the model and year of manufacture of the vehicle being tested. Some scanners are multifunctional, due to the ability to change the cartridge depending on the model of the vehicle being diagnosed (Ford, GM, Chrysler, etc.), others are tied to regional government requirements and are intended for use in specific areas of the world (Europe, Asia, USA, etc.).
With the introduction of the new generation of on-board diagnostics (OBD-II) systems that meet the latest environmental legislation, specially designed readers have begun to be manufactured. Some manufacturers have started producing scanners designed for use by amateur mechanics at home - ask in car accessory stores.
General description of the OBD system
Models of 1994 and 1995 are equipped with the first generation on-board diagnostics system. Beginning in 1996, Honda Motors began producing models equipped with the second generation self-diagnostic systems that meet CARB and EPA standards and are called OBD-II. The system includes several diagnostic devices that monitor individual parameters of the toxicity reduction systems and record detected failures in the processor memory in the form of individual fault codes. The system also checks sensors and actuators, monitors vehicle operating cycles, and provides the ability to freeze parameters and clear the memory block.
Reading of the OBD-II processor memory data is performed using a special scanner connected to the 16-pin diagnostic connector for reading the database (DLC), located under the dashboard on the driver's side of the car. All models of cars of the brands under consideration, starting from 1996, are equipped with a second-generation OBD-II self-diagnostic system. The main element of the system is an on-board processor, called an electronic control module (ECM) or a power control module (PCM).
The ECM/PCM is the brain of the engine management system. Input data is supplied to the module from various information sensors and other electronic components (switches, relays, etc.). Based on the analysis of data received from information sensors and in accordance with the basic parameters stored in the processor memory, the ECM/PCM generates commands to operate various control relays and actuators, thereby adjusting the engine operating parameters and ensuring maximum efficiency with minimum fuel consumption.
Maintenance of engine management/exhaust gas reduction components is subject to special extended warranty obligations. You should not attempt to independently perform diagnostics of ECM/PCM failures or replace system components before the warranty period expires – Please contact the specialists of the company's Honda service center.
Information sensors
Heated oxygen sensors (HO2S) – The sensor generates a signal, the amplitude of which depends on the oxygen content in the engine exhaust gases and the outside air.
Crankshaft position sensor (CPS) - The sensor is used in first generation self-diagnostic systems (OBD-I) and informs the ECM/PCM about the crankshaft position and engine speed.
TDC/Crankshaft Position/Piston Position Sensor (TDC/CKR/CYP) – This sensor is used in the second generation OBD-II systems. Based on the analysis of the information received from the sensor, the ECM/PCM determines the position of the piston of the first cylinder, determines the moments of fuel injection and ignition.
Crankshaft Fluctuation Sensor (CKF) – The sensor monitors changes in the engine speed. If the change in engine speed is outside the permissible range, a corresponding signal is sent to the ECM/PCM, which is interpreted by the module as evidence of a misfire.
Engine Coolant Temperature (ECT) Sensor – Based on the information received from the sensor, the ECM/PCM makes the necessary adjustments to the air-fuel mixture composition and ignition timing, and also monitors the operation of the EGR system.
Intake Air Temperature (IAT) Sensor – The ECM/PCM uses the information received from the IAT sensor to make fuel flow adjustments, spark advance settings, and control the operation of the EGR system.
Throttle Position Sensor (TPS) – The sensor is located on the throttle body and is connected to the throttle shaft. Based on the amplitude of the signal emitted by the TPS, the ECM/PCM determines the throttle opening angle (controlled by the driver using the gas pedal) and accordingly adjusts the fuel supply to the combustion chamber intake ports. Sensor failure or loosening of its fastening leads to injection interruptions and disturbances in the stability of idle speed.
Absolute pressure sensor in the pipeline (MAP) - The sensor monitors changes in pressure in the intake manifold associated with changes in engine speed and load, converting the received information into an amplitude signal. The ECM/PCM uses the information supplied by the sensor when adjusting fuel supply and setting the ignition timing. The range of change of the sensor output signal is from 1.0÷1.5 V with the throttle valve closed (deep vacuum), up to 4.0÷4.5 V with the valve fully open (low vacuum). The sensor is also located on the throttle body.
Vehicle Speed Sensor (VSS) – As its name suggests, the sensor informs the ECM/PCM of the current vehicle speed.
Fuel tank pressure sensor - The sensor is an integral component of the fuel evaporative emission (EVAP) system and is used to monitor the pressure of gasoline vapors in the tank. Based on the information received from the sensor, the ECM/PCM issues commands to operate the electromagnetic valves for purging the system.
Power Steering Pressure Switch (PSP) – Based on the information received from the switch sensor, the ECM/PCM increases the idle speed by activating the IAC sensor in order to compensate for the increasing loads on the engine associated with the operation of the power steering.
Knock sensor - The sensor reacts to changes in the vibration level associated with detonations in the engine. Based on the information received from the sensor, the ECM/PCM makes the appropriate adjustment to the ignition timing.
Transmission sensors – In addition to the VSS data, the ECM/PCM also receives information from sensors located inside or connected to the transmission. These sensors include the turbine shaft speed sensor, the ATF temperature sensor, and the gear selector sensor.
Air Conditioner Clutch Control Switch Sensor – When power is supplied from the battery to the electromagnetic valve of the A/C compressor, the corresponding information signal is sent to the ECM/PCM, which evaluates it as evidence of an increase in the load on the engine and adjusts its idle speed accordingly.
Executive devices
PGM-FI Main Relay (fuel pump relay) – The ECM/PCM activates the fuel pump relay when the ignition key is turned to the START or RUN position. When the ignition is turned on, the relay is activated to increase the pressure in the fuel system. The relay is located in the power distribution unit in the engine compartment of the vehicle. For a description of the fuel pump testing and replacement procedures, see Chapter Power and exhaust systems.
Fuel injection injectors – The ECM/PCM ensures individual activation of each injector in accordance with the firing order. In addition, the module controls the duration of the injector opening, determined by the width of the control pulse. The duration of the injector opening determines the amount of fuel injected into the cylinder. More detailed information on the operating principle of the injection system, replacement and maintenance of injectors is provided in Chapter Power and exhaust systems.
Ignition Control Module (ICM) – The module controls the operation of the ignition coils, determining the required basic advance based on the commands generated by the ECM/PCM. All vehicle models covered in this Manual use an ICM built into the ignition distributor, for more details see Chapter Engine electrical equipment.
Idle Air Control Valve (IAC) – The IAC valve controls the amount of air bypassed through the throttle valve when the throttle valve is closed or at idle. The ECM/PCM controls the opening of the valve and the resulting air flow. More information on the IAC valve can be found in Chapter 4.
Carbon adsorber purge valve – The charcoal canister purge solenoid valve is an integral part of the evaporative emission control system (EVAP) and, when triggered by the ECM/PCM, blows out the fuel vapors accumulated in the canister into the intake manifold for combustion during normal engine operation.
Reading fault codes
1. The service control connector is located under the instrument panel on the passenger side of the vehicle (see accompanying illustration).
2. To read the fault codes, it is necessary to short-circuit the connector terminals with a jumper wire and monitor the readings of the "Check Engine" indicator lamp built into the vehicle's instrument panel (valid for all models). A special diagnostic reader can only be connected to the 16-pin Diagnostic Link Connector (DLC), located on the left side under the vehicle's instrument panel (see accompanying illustration).
3. To view the fault codes stored in the ECM/PCM memory, install a jumper in the service control connector (see illustration for paragraph 1), then turn on the ignition by turning the key to the ON position. If the processor memory contains codes of the malfunctions that have occurred, they will begin to be sequentially displayed by the "Check Engine" indicator lamp on the vehicle's instrument panel. The first digit of the two-digit code is displayed by long flashes of the lamp, the second by short flashes (for example, one long inclusion followed by six short ones corresponds to code 16).
Note: If more than one code is stored in the control module memory, they will be displayed one after the other, then after a pause the display of the codes will be repeated.
List of OBD-I diagnostic system trouble codes
| Code number | Chain or system | Actions to eliminate the cause of failure |
| 1 | ECM/PCM faulty | Check the ECM/PCM electrical connector, if no signs of contact failure can be found, take the vehicle to a service station for detailed diagnostics |
| 3 and 5 | Oxygen content | Check the oxygen sensor, its heater and the wiring circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 4 | MAR | Check the MAP sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 6 | Investigative Committee of Russia | Check the CKP sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 7 | TPS | Check the TPS sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 8 | TDC | Check the TDC sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 9 | CYP cylinder #1 | Check the CYP sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 10 | IAT | Check the IAT sensor and its electrical circuit (see Checking the health and replacing the throttle position sensor (TPS)) |
| 12 | EGR | Check the condition of the system hoses, the EGR valve opening value sensor and the EGR valve (see Checking the condition and replacing the intake air temperature (IAT) sensor) |
| 13 | Barometric pressure | Take the car to a service station for inspection |
| 14 | IAC valve | Check the IAC valve and the idle speed control system (see Chapter Power and exhaust systems) |
| 15 | Ignition output signal | Check the ignition system (see Chapter Engine electrical equipment) |
| 16 | Injection injector | Check the fuel system and fuel injectors (see Chapter Power and exhaust systems) |
| 17 | VSS | Take the car to a service station for inspection |
| 19 | Shut-off electromagnetic valve | On models with AT, check the condition of the solenoid valve (see 4-speed and continuously variable automatic transmissions (AT and CVT)) |
| 20 | ELD | Check the ELD system (see Checking the condition and replacing the TDC/crankshaft position/piston position sensor in the engine cylinders (TDC/CKR/CYP)) |
| 21 | Adjustment of timing phases and valve lift solenoid | See VTEC Solenoid Checks, Chapter Engine Repair Without Removing It From The Car - Civic Models |
| 22 | Timing phase adjustment and pressure sensor | See VTEC Pressure Sensor Tests, Chapter Engine Repair Without Removing It From The Car - Civic Models |
| 30 | Signal A A/T FI (models with AT) | Take the car to a service station for inspection |
| 41 | Oxygen sensor heater | Check the heater voltage signal for correct operation (see Chapter Power and exhaust systems) |
| 43 | Fuel supply system | Check the fuel pressure and the condition of the regulator (see Chapter Power and exhaust systems), also check the oxygen sensors for signs of vacuum loss |
| 48 | Heated l-probe | Check the heater voltage signal for correct operation (see Chapter Power and exhaust systems) |
List of OBD-II diagnostic trouble codes
| Code number (number of MIL flashes) | Possible reason for refusal |
| P0106 (5) | MAP sensor/engine efficiency issues |
| P0107 (3) | MAP sensor low input |
| P0108 (3) | MAP sensor high input |
| P0111 (10) | IAT Sensor/Engine Performance Issues |
| P0112 (10) | IAT Sensor Input Low |
| P0113 (10) | IAT Sensor High Input |
| P0116 (86) | ECT sensor/engine efficiency issues |
| P0117 (6) | ECT sensor low input |
| P0118 (6) | ECT sensor high input |
| P0122 (7) | TPS Sensor Low Input |
| P0123 (7) | TPS Sensor High Input |
| P0131 (1) | Primary Heated I-Probe Circuit Low Voltage (oxygen sensor 1) |
| P0132 (1) | Primary Heated I-Probe Circuit High Voltage (oxygen sensor 1) |
| P0133 (61) | Slow response of the primary heated l-probe (oxygen sensor 1) |
| P0135 (41) | Malfunction in the primary l-probe heater circuit (oxygen sensor 1) |
| P0137 (63) | Low Voltage Secondary Heated I-Probe Circuit (oxygen sensor 2) |
| P0138 (63) | High Voltage Secondary Heated I-Probe Circuit (oxygen sensor 2) |
| P0139 (63) | Slow response of secondary heated l-probe (oxygen sensor 2) |
| P0141 (65) | Malfunction in the secondary l-probe heater circuit (oxygen sensor 2) |
| P0171 (45) | Over-lean mixture |
| P0172 (45) | Over-enrichment of the mixture |
| P0300 | Random misfires |
| P0301 (71) | Misfire in cylinder #1 |
| P0302 (72) | Misfire in cylinder #2 |
| P0303 (73) | Misfire in cylinder #3 |
| P0304 (74) | Misfire in cylinder #4 |
| P0325 (23) | Malfunction in the knock sensor circuit |
| P0335 (4) | Malfunction in the CKP sensor circuit |
| P0336 (4) | SCR sensor/engine output efficiency issues |
| P0401 (80) | EGR flow too low detected |
| P0420 (67) | Insufficient efficiency of the catalytic converter |
| P0441 (92) | EVAP purging is not effective enough |
| P0452 (91) | Fuel Tank Pressure Sensor Low Input (eVAP system) |
| P0453 (91) | Fuel Tank Pressure Sensor High Input (eVAP system) |
| P0500 (17) | Malfunction in VSS circuit |
| P0501 (17) | VSS Sensor/Engine Performance Issues |
| P0505 (14) | Malfunction in IAC sensor circuit |
| P0700 (70) | AT |
| P0715 (70) | AT |
| P0720 (70) | AT |
| P0725 (70) | AT |
| P0730 (70) | AT |
| P0740 (70) | AT |
| P0753 (70) | AT |
| P0758 (70) | AT |
| P1106 (13) | BARO sensor/engine efficiency issues |
| P1107 (13) | BARO sensor input low |
| P1108 (13) | BARO sensor high input |
| P1121 (7) | Throttle opening is greater than expected |
| P1122 (7) | Throttle opening is greater than expected |
| P1128 (5) | Absolute pressure in the pipeline is lower than expected |
| P1129 (5) | Absolute pressure in the pipeline is higher than expected |
| P1162 (48) | Malfunction in the primary l-probe circuit (oxygen sensor 1) |
| P1163 (61) | Primary l-probe response too slow (oxygen sensor 1) |
| P1164(61) | Primary l-probe/engine efficiency problems |
| P1165 (61) | Primary l-probe/engine efficiency problems |
| P1166 (41) | Malfunction in the primary l-probe circuit (oxygen sensor 1) |
| P1167 (41) | Malfunction in the primary l-probe heater circuit (oxygen sensor 1) |
| P1168 (48) | Primary l-probe LABEL input signal low (oxygen sensor 1) |
| P1169 (48) | Primary l-probe LABEL high input signal (oxygen sensor 1) |
| R1259 (22) | VTEC system malfunction |
| R1297 (20) | ELD Input Low |
| R1298 (20) | ELD Input High |
| P1300 (-) | Random failure |
| P1301 (71) | Misfire in cylinder #1 |
| P1302 (72) | Misfire in cylinder #2 |
| P1303 (73) | Misfire in cylinder #3 |
| P1304 (74) | Misfire in cylinder #4 |
| R1336 (54) | Instability of CKF sensor readings |
| P1337 (54) | No signal from CKF sensor |
| R1359 (8) | TDC sensor disconnected |
| R1361 (8) | TDC sensor readings instability |
| R1362 (8) | No signal from TDC sensor |
| R1381 (9) | CYP sensor readings are unstable |
| R1381 (9) | No signal from CYP sensor |
| R1456 (90) | There are fuel vapor leaks in the gas tank (EVAP) |
| R1457 (90) | There are fuel vapor leaks in the charcoal canister (EVAP) |
| R1491 (12) | EGR valve opening degree is insufficient |
| R1498 (12) | EGR valve opening sensor gives too high signal |
| R1508 (14) | Malfunction in IAC valve circuit (1) |
| R1509 (14) | Malfunction in IAC valve circuit (2) |
| P1607 (-) | ECM/PCM Internal Circuit Malfunction |
| R1655 (30) | There is an open or short circuit in the TMA/TMB signal line |
| P1705 (70) | AT malfunction |
| P1706 (70) | AT malfunction |
| R1753 (70) | AT malfunction |
| R1758 (70) | AT malfunction |
| R1768 (70) | AT malfunction |
| R1785 (70) | AT malfunction |
| P1790 (70) | AT malfunction |
| R1791 (70) | AT malfunction |
| R1793 (70) | AT malfunction |
| P1870 (70) | AT malfunction |
| R1873 (70) | AT malfunction |
| R1879 (70) | AT malfunction |
| R1885 (70) | AT malfunction |
| R1886 (70) | AT malfunction |
| R1888 (70) | AT malfunction |
| P1890 (70) | AT malfunction |
| R1891 (70) | AT malfunction |
Clearing ECM/PCM memory
When a fault code is entered into the ECM/PCM memory, the "Check Engine" indicator lamp on the vehicle's instrument cluster lights up. The code remains stored in the module's memory until the power supply is disconnected. To clear the control module's memory, remove the BACK-UP fuse from the mounting block located on the right side of the engine compartment for 10-15 seconds (see Chapter On-board electrical equipment).
Note: Removing the fuse will also turn off the radio and erase its settings.