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Written By: Gibson Hull
March 30, 2025
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The check engine light was showing on the dash, the computer screamed engine malfunction, and it was not running as smoothly as Charlie was accustomed. BMWs can be costly to own because of the cost of maintenance alone. But a bit of research, some patience, some know-how, and you can easily tackle this job at home by yourself. Even better, tackle it with a friend.
Step 02. Plug diagnostic tool into OBDII port. There is an OBDII port to plug in an engine diagnostic tool into most if not all automobiles sold in the US since 1996 when Congress required standardization of engine diagnostics.
Step 03. Run diagnostic and research codes and faults. Reading engine diagnostics could take a few books much less a small part of a humble blog post. Keep an eye out for a future post on the ins and outs of engine diagnostics. Today we are getting a P0202 code for “Cylinder 2 Injector ‘A’ Circuit”. The primary culprit after digging into some online research is bad fuel injectors. They are known to go bad, and it is likely time to replace them anyway.
Step 04. Disconnect the battery. The BMW 135i battery lives in the trunk because weight distribution! Where else would it go alongside a straight 6 and 2 turbos in such a tiny engine bay? Anytime you are working on your car it is a good idea to disconnect the battery for safety. This is especially important when working on electrics or around the engine. Simply loosen the nut holding the negative battery cable and remove it from the battery, taking care to ensure that it will not find a way back to the battery terminal on its own.
Step 05. Remove plastic covers. Self explanatory, but we need to get all of these plastic covers out of the way to get to the engine. Hunt for the various screws and fasteners holding each to the car and remove. These european cars use a lot of torx fasteners, so grab a good set or torx bits and sockets.
Step 01. Run engine diagnostic.
Step 03. Run diagnostic and research codes and faults.
Step 04. Disconnect the battery.
Step 05. Remove plastic covers.
Step 07. Remove injector wiring harness nuts. Remove the nuts holding the wiring harness wires on each injector.
Step 08. Remove the three injector braces. There are three injector braces held on by a single torx bolt each. Each brace holds two injectors. It starts to get tricky as you get to the back of engine which begins to disappear at the back of the engine bay, but stay patient! You can do this.
Step 08a. See the brace and bolt pictured. Say cheese.
Step 09. Remove fuel lines. There is a short fuel line from the fuel rail to each injector. Carefully remove each fuel line with a line wrench or even more carefully with a normal box end wrench. The fuel is still under some residual pressure, so have a towel handy to gather any that escapes, and be careful with it.
Step 10. Next we need an injector puller. This is a special slide hammer that threads onto each injector and allows you to reverse hammer the injectors, knocking and pulling them free of their tight mechanical seat. This job would be almost impossible without this tool.
Step 06. Remove ignition coil plugs and harness.
Step 07. Remove injector wiring harness nuts.
Step 08. Remove the three injector braces.
Step 08a. See the brace and bolt pictured. Say cheese.
Step 09. Remove fuel lines.
Step 10. Next we need an injector puller.
Step 12. Pull old injectors free. It takes a while sometimes. These suckers are IN THERE.
Step 13. Compare old and new. This Beamer is about to be flush with fuel.
Step 14. Record new Injector numbers. Record the two numbers on the side of each injector and the number of the cylinder in which it will be installed. This will be important when we identify each injector in the 135i’s computer later.
Step 11. Install injector puller onto each injector and remove.
Step 12. Pull old injectors free.
Step 14. Record new Injector numbers.
Step 16. Rejoice that the tool is retrieved.
Step 17. Install new Injectors, braces, wires, lines, and coil plugs. Begin installing the new injectors, two at a time, install the brace, and torque it to spec. Reinstall fuel lines, connect injector wires, and tighten securing nut. Replug the coils.
Step 18. Test start the engine and code injectors with program. Fire the engine and see how the new injectors react. After a bit of stuttering as the fuel refilled and pressurized, the little 135i roared back to life. We used Bimmercode, a third party program for programming BMW engine control modules. There are a number of other options available as well. All you need to do is take the numbers you recorded from each injector and tell the computer the new number for each injector.
Step 15. Retrieve tool dropped into the abyss.
Step 16. Rejoice that the tool is retrieved.
Step 18. Test start the engine and code injectors with program.
Step 19. All done, happy Charlie with a running car!