TCU/TCM Fix Tutorial
     

TCU/TCM Fix Tutorial How to fix your TCM and save $500US, then donate the money you saved to charities that will self empower others.

Problem: Won't start, the relay won't click and no fuel pump sound.

1. Connect your black probe of your multimeter to terminal 2. Connect your red probe to terminal 1. There should be battery voltage. If not then check the ECU fuse.
   
   
   
2. Turn the ignition switch to ON. Connect your black probe of your multimeter to terminal 2. Connect your red probe to terminal 5. There should be battery voltage. If not then check the fuse or the ignition switch.

   
   Read more...
   

A few images are added in the main relay replacment page. See
http://techauto.awardspace.com/mainrelaydefine.html

A few images are added in order to get an insight into the problem and to better prepare yourself. 

Above: The end result of arcing. How to replace the ignition switch or troubleshoot (Honda, Acura)

Ever wonder why there isn't an easy way to check the condition of your ignition switch quickly and easily. The answer is because it's so easy they don't want you to know. Today, a diagnose can run you $89 an hour. They don't want you to know the secret. Well, the secret is out.  You can check the condition of your ignition switch by checking for power at the coil. The voltage that you see can determine the condition of the ignition switch. If the voltage is at 12V or higher, then that is sign of a good ignition switch. If it's 12V or under, it is an aging switch, but doesn't necessarily mean it's a defective switch.  Begin by checking for power at the ignition coil (terminal A) with the ignition switched to ON. There should be battery voltage. 

                 
For the 88-89 Accord coil, see this [image.] For the civic coil see this [image].

If there is no power then check the ignition fuse (most often labeled IG...) in the engine bay fuse box. If the fuse is fine then continue below. 

How to replace the ignition switch or troubleshoot (Honda, Acura)

ECU code 15 which is "Ignition Output Signal." A sign of failing igniter. The dreaded code no one wants to know. To learn more see what it means ignition.html#code15

Ever wonder why flowcharts are hard to search or translated on the fly to another language of your choice? Here is a text based flow chart for those who need to know if their main relay is dead just a glance. To search hit Cntrl+F on your keyboard.

Can be found here.  mainrelay.html#Troubleshoot3

 

	Car Won't Start				Main relay troubleshooting for most Honda/Acura PGM-FI relay and harness

	Turn the ignition switch to ON.

	Does the check engine light go on then off?				The ignition switch and ECU is okay.

	Is there a relay click when the check engine light is on?				Main relay is dead.

	Is there a relay click when the check engine light is off?				Main relay is dead.

	Does the fuel pump whirl for 2 seconds when the check engine light is on?				Fuel pump may be dead. Check the fuel pump.

	Main relay is OK. Turn ignition off.

	More troubleshooting can be found at mainrelay#Trbsh3

 

Could this happen to you. Rarely would we find our door jams shut and can't get in or get out. You could remove the door panel and poke around or you could drill a single hole painlessly and the door pops open. Or... maybe, you'll need more than just a single hole. Here's a step by step guide to solving the problem . See http://techauto.awardspace.com/doorproblem/index.html#latch.

Ever wonder why your radiator fan still won't come on after replacing the most likely bad part? Maybe it's a the wiring circuit or other bad unexplained part that is the problem. Here's how to find that dreaded fault in your cooling system circuit once and for all. It's a unique (but known in the trade) step by step guide to help solve any Honda with a relay. See http://techauto.awardspace.com/overheating.html#finaltroubleshoot.

Ever wonder how to properly use a test light to pierce a wire without worrying about that dreaded copper corrosion? Test light peircing could be complicated to some, but it works better than a wire-peircing-probe with practice. Here's a "how to."  See http://techauto.awardspace.com/ignition.html#3.

What to do when your Honda overheats. Once in your lifetime, an overheating will happen to you. Learn to protect your investment. See overheating.html#Solutions.

Transmission D4 light and won't shift solution. See transmission.html.

How to replace the fan timer.

How to prevent your plastic radiator from cracking using epoxy, a couple steel plates or zip ties.

Learn more >>

Do you have questions regarding transponder type immobilzers?

Auto Theft problem: How to protect your ignition switch.

 

Thanks to Steve for drawing this picture for us. See what the parts do here.

 

Thanks to Steve for drawing this picture. This helps us see why the ignition switch contacts are worn. A real image would work but then photographic images can't be printed.

Main relay FAQ section added for easy reading.

Main Relay Technical details

What is the main relay?

The main relay (which consists of two relays that are remotely operated as a switch)  is a device that opens or closes under control of another device usually the ignition switch or ECU. The main relay opens and closes the fuel pump, the fuel injection and ECU. 

How do I identify the main relay? 

Look for RELAY ASS'Y. MAIN

 

Technical Details

Desoldering with a desoldering iron.

1.) Press the vacuum pump push-bulb. Apply the desoldering iron tip so that the terminal penetrates within its orifice.
2.) When the solder liquefies, start gently to rotate the desoldering tip so that the component’s terminal can be eased away from the sides.
3.) Release the vacuum pump push-bulb just long enough to suck the solder.

Note: If any solder remains are left on any terminal after attempting to desolder it, resolder it with fresh solder and repeat the desoldering process.

More at mainrelay solder page

---

 

Replacing key cylinder on 86-89 Accord.

Note: These steps are not for the novices. They are here for our technical member's reference since it's one of the FAQ. If you don't understand then post a comment. 

Steps:

1. Turn switch to ON (I) pin button down. Pull cylinder out.
2. Please go to igniton switch to read more...

Removing the tumbler from the cylinder

1. To eject the tumbler from the cylinder.
2. Remove spring loaded key lock cover on cylinder.
3. Stick key inside. Twist key to opposing direction.
4. Push cylinder out from the other end.

 

Removing the bolt from the steering column.

1. Center punch the bolt at 3'O clock. 
2. Slightly angle the center punch and punch the bolt out counterclockwise.
   More...
   
   View at http://techauto.awardspace.com/ignitionswitch.html#key

    

 

WHT BLK/YEL BLK/WHT OFF       ON (II)     START (III)    Measure continuity as specified.

Troubleshooting at the harness:

Steps:

1. Follow the harness from ignition switch to the fuse box. Disconnect the ignition switch wire harness connector from the fuse box. 
2. Touch the probe of the a DMM to WHT. 
3. Touch the other probe of the a DMM to BLK/YL. There should be continuity when the ignition is switch to "ON."
4. Remove the probe from BLK/YL (Do not remove the probe of the a DMM to WHT.) 
5. Touch the other probe of the a DMM to  BLK/WHT. There should be continuity when the ignition is switch to "START."
6. If you do not find the continuity as specified replace the ignition switch.
7. If you do not find the wire colors as specified on your ignition switch, stop here and consult your service manual.

 

 

 

Troubleshooting at the switch:

Steps:

1. Connect the negative end of the a DMM (test light okay) to ground (any metal part of the steering column) and the other to WHT. There should be battery voltage.
2. Connect the negative end of the a DMM to ground (any metal part of the steering column) and the other to BLK/YL. There should be battery voltage when the ignition is switch to "ON."
3. Connect the negative end of the a DMM to ground (any metal part of the steering column) and the other to BLK/WHT. There should battery voltage when the ignition is switch to "START."
4. If you do not find the continuity as specified replace the ignition switch.
5. If you do not find the wire colors as specified on your ignition switch, stop here and consult your service manual.

 

Note: Puncturing the wires to check for voltage is not recommended since the internal wires may exposed to the environment. With every puncture the wire should be sealed with RTV silicone. Avoid damaging the female connector terminals, do not insert your probe deep into the female connector, instead lightly touch the terminal's copper surface. 

Note: This diagnose does not cover accessories such as the blower motor and etc. This is because they are not mission critical and are simply luxury items which requires a unique set of procedures beyond the scope of this page. 

  Location ignition switch