January 1, 0001

Known Honda Problems

This page contains some of the known problems with Honda Civics that I have personally run into. Some of these problems aren’t well known to those outside the Honda community so your local mechanic could spend days trying to find some of these.

Main Fuel Relay - Vehical Speed Sensor - Oxygen Sensors

Main Fuel Relay

This Honda Civic problem was potentially the most frustrating problem I have ever had with a car, period. Basically the Main Fuel Relay that controls power to the fuel pump stops giving it power at what appears to be completely random times. This is supposedly cause by cold solder cracks in the PCB. When I eventually found out that this problem existed the mechanic at the time opened the relay up to have a look and everything looked fine. We still replaced it though and that fixed the problem.

The problem slowly gets worse and worse with the frequency of non-starts getting higher and higher. Diagnosing wasn’t easy. A non-starting car can be caused by lots of things, but basically it boils down to not having enough fuel, air or spark (assuming that it is cranking over). If a fuel pressure gauge had been used during the diagnosis it might not have taken so long to diagnose. However, knowing what was causing the fuel pump not to run would have been a nightmare to find. Thank goodness for the interweb thingy.


  • The car would intermitently just decide not to start. The starter motor would crank over but the engine would not fire.
  • It was worse in summer when the internal temperature in the car was high.
  • Once the car started there were no problems.
  • No ECU Error Codes were thrown.


The follow tips can help diagnose whether or not your symptoms are caused by a faulty Main Fuel Relay.

  • When you switch the key to ON there is normally a slight hissing noise and a then a click. This is the fuel pump pressuring the fuel supply line. If you hear this noise and the car starts, great. If the Main Fuel Relay is causing problems you won’t always hear this noise and when you don’t, the car won’t start.
  • Switching the car to OFF and then ON repeatedly helps to get it started.
  • Remove the Main Fuel Relay (leaving it connected of course) so you can handle it. Give it a whack. If the car is more likely to start after you whack it, then you may have a faulty relay.

Vehicle Speed Sensor

This Honda Civic problem is quite frustrating. Every now and then while driving along the speedo just stops working. This in itself isn’t all that annoying, but when you remember that VTEC won’t engage unless the car is doing or 20 or 30km/h it can ruin any spirited driving outing.

The problem doesn’t really seem to get any worse once it starts, it just carries on happening. If the speedo stays out long enough eventually a code will be thrown indicating the VSS. At first I couldn’t really see how a VSS could go bad, but apparently it is quite common. I have yet to replace the VSS, but I am just going to replace it with a second hand one…new ones are quite expensive.

Oxygen Sensors

This Honda Civic problem was very, very puzzling and took some time searching on the interweb to finally figure out what the problem was likely to be. When I did the B16A Engine Swap I carefully labelled which Oxygen Sensor went to which set of primaries in the exhaust. However, it doesn’t appear like I was careful enough. Somehow they managed to get swapped around somehow.

The PW0/PR3 ECU in the Honda Civic SiR uses one Oxygen Sensor to monitor the fueling for two cylinders. So, if you get them around the wrong way the computer is going to lean out two cylinders and richen up the other two since the readings are all reversed.


  • The car would idle fine.
  • The car would hestitate on the motorway when starting to accelerate from a constant speed.
  • Fuel economy decreased, but not substantially.


  • Unplugging the Oxygen Sensors rectified the problem. With the Oxygen Sensors unplugged the car would always run in open loop mode using predefined maps for the fuelling based on other sensors like the throttle position, and rpm.
  • Putting a volt meter on the Oxygen Sensors while the car was idling and up to temperature showed one output reading high (~0.9V) with the other one reading low (~0.3V). These readings would remain reasonably constant.
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