ENG: CEL Diagnostics & Basic Repair

[ExplodingCake]

Guide to most common 90-93 Honda Accord CEL diagnostics.

For information regarding about pulling the codes please refer to Aero's guide at this link.
http://www.cb7tuner.com/vbb/showthre...&highlight=CEL

ECU reset procedure: Reset the ECU by pulling off the negative battery terminal and removing the back-up fuse for 15 minutes. After the time frame has passed install back everything. Turn on the car and let it sit for 5 minutes and you're all set.



CODE 0 – (Electronic Control Unit) Faulty ECU

ECU – main purpose controls one or more electrical subsystems of a vehicle.

What to do: What you might want to do first before thinking of replacing it is check the electrical connections carefully. ECU is located under the passenger side kick panel. Pull out the carpet and the ECU will be revealed. With great luck the connections might be loose. If this exercise does not bring success , a replacement ECU will be your next move.


CODE 1 – Oxygen Sensor.

Oxygen Sensor – measure the proportion of oxygen.

What to do: Check your oxygen sensor. For F22A1 engines the Oxygen Sensor is located right into the upper part of the exhaust manifold. Remove the heat shield to fully reveal it's location. For F22A4/6 engines , the oxygen sensor is located right before the catalytic converter on the exhaust manifold down pipe.

To determine if the oxygen sensor really failed , turn on the car and let it idle & acquire a voltmeter. Disconnect the oxygen sensor connector and do this exercise. Increase the idle speed of the vehicle and check the voltage reading. The reading should be in between 0.5 volts to 1.0 volts. When you decrease the idle the voltage reading should be in between 0.0 to 0.4 volts. If the oxygen sensor fails within these exercise , replace it with and OEM replacement.

NOTE: NGK (NTK) & Denso are highly recommended replacement parts.

Oxygen Sensor replacement procedure: It's recommended that a special socket made for oxygen sensor to be used in order to ease the procedure. Unscrew the oxygen sensor and dispose of properly. Before installing the new oxygen sensor it is recommended to coat the threads with an anti-sieze compound to make future removal easier. Connect the oxygen sensor pigtails. Before running the vehicle it is recommended to reset the ECU.


CODE 3 & 5 – (MAP) Manifold Absolute Pressure.

Manifold Absolute Pressure – it is used by the ECU to control fuel delivery and ignition timing.

What to do: Check the hose that goes in to the MAP sensor. If there is deterioration or any signs of defects, it should be replaced. All electrical connectors regarding the MAP sensor should be check and see if they are connected properly. Failure of these exercise will result in replacement of the MAP sensor.

To replace the MAP sensor disconnect any electrical connections connecting to the MAP sensor. Remove the vacuum control box located on the passenger side firewall right next to the engine bay fuse box and remove the MAP sensor. Installation is reverse of removal. Before running the vehicle it is recommended to reset the ECU.


CODE 4 – Crank Angle Sensor.

Crank Angle Sensor – monitors the rotation of the crankshaft

What to do: Make sure the electrical connectors are on tight and properly connected. Make sure the position of the distributor is right that way it's supposed to be. If all else fails, replace the distributor and reset the ECU.


CODE 6 – Coolant Temperature.

Coolant Temperature – a resistor which sends signals in accordance with change in temperature.

What to do: Remove and replace the sensor with a new part. To remove the sensor , unlock the locking tab then unplug the green electrical connector located under the distributor and carefully unscrew the sensor. Be advised that coolant will leak out during this process and must install the new one ASAP. Before installing the new part , it is recommended to wrap the new sensor with Teflon tape to prevent leakage. Plug back the electrical connector and reset the ECU.


CODE 7 - Throttle Position Sensor (TPS).

Throttle Position Sensor – monitors the position of the throttle.

What to do: Replace the TPS. The TPS is located on the throttle body. Carefully unplug the electrical connector on the TPS and remove the TPS. Installation is reverse of the removal process. It's is recommended to reset the ECU as well.

Please refer Cokinut's guide to setting the TPS.
http://www.cb7tuner.com/vbb/showthread.php?t=16374


CODE 8 – Top Dead Center Position

Top Dead Center – Position of a piston farthest from the crankshaft. Position of a piston closest to the crankshaft is defined as bottom dead center.

What to do: Make sure the electrical connectors are on tight and properly connected. Make sure the position of the distributor is right that way it's supposed to be. If all else fails, replace the distributor and reset the ECU.

[ExplodingCake]

CODE 9 – Number 1 Cylinder Position

What to do: Make sure the electrical connectors are on tight and properly connected. Make sure the position of the distributor is right that way it's supposed to be. If all else fails, replace the distributor and reset the ECU.


CODE 10 – Intake Air Temperature Sensor

Intake Air Temperature Sensor – monitors air temperature getting inside the intake manifold.

What to do: Replace the IAT sensor. It is located on the intake manifold. To remove the IAT sensor you must unplug the electrical connector and remove the screws that hold the sensor to the intake manifold. Remove the IAT sensor and replace with a new one. Installation is reverse of removal. It is also recommended to reset the ECU.


CODE 12 – Exhaust Gas Recirculation (EGR).

Exhaust Gas Recirculation – it reduces nitrogen oxides by recirculation exhaust gases through the EGR valve and into the combustion chamber.

What to do: Before proceeding on EGR valve replacement , sometimes just cleaning the EGR valve and ports may solve the problem. If that exercise failed , proceed on replacing the EGR valve. Start the vehicle and let run to it's normal temperature. Once that's done , disconnect the number 16 hose on the EGR valve. The EGR valve is located on the left side of the fuel rail. There should be no vacuum once the hose is disconnected. If there is vacuum present , install a compact vacuum pump and apply to the valve to check if the engine stalls. If the EGR valve does not hold the vacuum , replace the EGR valve. To replace the EGR valve , unplug the electrical connector. Remove the nuts that holds the EGR valve in place. Carefully lift the EGR valve and clean the mating surface. Install new EGR gasket and install the new EGR valve. Tighten it in place securely and plug in the electrical connector. Reset the ECU and start the vehicle.


CODE 13 – Atmospheric Pressure

Atmospheric Pressure – it is the pressure of atmosphere at any given point in the earth.

What to do: This is very uncommon but it is known that vehicles at high altitude may or may not get this certain code. It is best to bring the car at the certified service center for further diagnostics.


CODE 14 – Idle Air Control Valve (IACV).

Idle Air Control Valve – monitors and changes the amount of air to be bypassed into the intake manifold. It is activated by the vehicles ECU by determining the engine load.

What to do: IACV is located on the intake manifold close the fuel rail. Disconnect the electrical connector on the IACV and acquire an ohmmeter and measure the resistance. Reading should be in between 8 and 15 ohms. While doing this check for continuity , if there is continuity present , replace the IACV immediately.

Another way to solve CODE 14 is to remove the IACV , grab a brake cleaner and clean the IACV. Install the IACV and reset the ECU. If it does not bring any great success , replace the faulty IACV. Reset the ECU once again.


CODE 15 – Ignition Output Signal.

Ignition Output Signal – provides control of ignition timing by determining the optimum timing using a microchip in response to engine speed , throttle position , coolant temperature and vacuum pressure.

CAUTION: When replacing components on the ignition , it is HIGHLY RECOMMENDED that you disconnect the negative battery terminal.

What to do: Please note that 90-91 Models have an internal ignition coil while 92-93 Models have an external ignition coil. It is recommended to acquire an ignition tester. On this process, spark plug wires should be tested to determine the problem. Pull out one spark plug wire one at a time and connect the tester. If there is enough power to the wires , sparks will be visible to the electrode. If this process bring great success proceed on testing the ignition coil and igniter. Otherwise replace the spark plug wires.

In order to test the ignition coil for 90-91 models , remove the distributor cover and rotor. Using an ohmmeter touch the electrical probes of terminal A & B of the ignition coil. It should read 0.6 to 0.8 ohms. If your readings are nowhere these specifications , replace the ignition coil. To replace the ignition coil , remove the screws form the primary terminal and the screws from the coil and slide the coil out. Installation is reverse of removal.

In order to test the ignition coil for 92-93 models , disconnect the electrical connector from the ignition coil tower. Using an ohmmeter touch the electrical probes of terminal A & B of the ignition coil. It should read 0.6 to 0.8 ohms. If your readings are nowhere these specifications , replace the ignition coil. To replace the ignition coil unplug the primary electrical connector and remove the ignition coil wire. Remove the two bolts that are located on the mounting bracket and remove the coil. Installation is reverse of removal.

It is also recommended to reset the ECU.


CODE 16 – Fuel Injectors.

CAUTION: Gasoline is ultimately flammable , use high precaution and have a fire extinguisher in hand in case of emergencies.

Fuel Injectors – supplies fuel to the combustion process.

What to do: While the engine warm and running , unplug one fuel injector electrical connector and see if the engine speed changes. If a certain injector fails to change the idle speed , check the electrical resistance. If all fuel injectors change in the same idle speed , injectors are working correctly.

To check fuel injector resistance , using an ohmmeter. Turn the vehicle off and unplug each fuel injector electrical connectors. Resistance should read between 1.5 to 2.5 ohms. If the acquired reading is not within range , replace the fuel injector.

To replace the fuel injector you must relieve the fuel pressure and disconnect the negative battery terminal. In order to relieve fuel pressure , you'll need two wrenches on this process. One for the loosening the service bolt and second for holding the banjo bolt. Be advised that fuel will come out during this process , it is good to have lots of shop towels in hand. Loose the service bolt to relieve pressure , once it's relived remove the service bolt and install the bolt back with a new washer. After the relieve process , you can now remove the fuel injectors. To remove the fuel injectors , unplug each electrical connector , detach the vacuum hose and return hose from the fuel pressure regulator. Remove the ground cable located on the fuel rail and remove the fuel feed line. Remove the mounting nuts and remove the fuel rail from the injectors. You can now remove the injectors. Install new injectors with new seal rings , o-rings and cushion rings. Installation is reverse of removal.

[ExplodingCake]

CODE 17 – Vehicle Speed Sensor (VSS).

Vehicle Speed Sensor – monitors speed reading and sends signals to the speedometer.

What to do: Replace the vehicle speed sensor.

Please refer to this image regarding the VSS location.



CODE 20 – Electric Load Detector (ELD)

Electrical Load Detector – detects excess amps in the electrical circuits.

What to do: The ELD is located on the engine bay fuse box. Using an ohmmeter , measure the electrical resistance. Remove the electrical connector and turn the ignition key to ON position. Measurements should be within 4.5 to 5.0 volts. Tuning the headlights on should give you a reading of approximately 2.0 volts. If your acquired measurements does not fall within range , replace the ELD assembly. This requires replacing of the whole engine bay fuse box.


CODE 30 & 31 – A/T Signal A& B

This particular codes fall under vehicles with automatic transmissions only. It is best to bring the vehicle to a certified repair shop.


CODE 41 – Oxygen Sensor Heater

Please refer to CODE 1 for diagnostics , repair and replacement.


CODE 43 – Fuel Supply System

What to do: Most common faulty part is the fuel pump. To check if the fuel pump works on not , turn on the ignition key and hear if the fuel pump makes a humming sound. It is better to double check for sound. If you do not hear a humming sound , replace the fuel pump. To replace the fuel pump , it requires dropping of the gas tank to the ground. Once the tank is removed , replace the fuel pump. Installation is reverse of removal.

"43 is gonna be the hardest to diagnose/write up, but I had a 43 a little while back and I changed my O2 with OEM and it fixed it" - accordaffair






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Editing of this thread will continue. Now I'm tired and hungry. I need a sandwich and root beer.
If you guys are willing to share any bright ideas , experiences on certain codes please pot em up and I will add them.

I did this write-up with the best of my knowledge. No direct copy and paste without credit.

[90_ACCORD]

i just threw number 43 so what are all the possible problems this could be

[ExplodingCake]

i just threw number 43 so what are all the possible problems this could be

oxygen sensor