DIY PGMFI Diagnostics - Code 8 TDC

[ECU-MAN]

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!


No part of this DIY is to be reproduced with out acknowledgment of the site and author it came from, ie me and ozhonda.com. Do not rip parts off and claim them as your own.




TDC Sensor "Top Dead Centre". The TDC sensor is commonly located on the side of the head, inside the Distributor. Not to be confused with the CKP or CYP sensor that is also located in the distributor, or in its own housing driven by the exhaust camshaft. . The TDC is a magnetic pulse generator type of sensor. The ECU monitors the TDC to determine TDC of each cylinder for starting. Also acts as a backup to the CYP and CKP.

Below is a picture of an CKP CYP TDC sensor in a B16A2 Distributor. The yellow arrow is pointing to the TDC magnetic pickup and the pulsar







Aim:

Diagnose code 8.






Required:

Basic Testing

- Digital Multi Meter
- Tachometer ( vehicle tacho can be used )
- paper clip


Advanced Testing

- all the above
- oscilloscope or wave form viewer


Symptoms

For a faulty TDC sensor to trigger code 8, you will more than likely get the engine light come on and the car will go into limp mode, Limp mode is a preset fuel and ignition map running on a backup processor in the ECU. Limited to about 3500rpm and a rich mixture to protect the engine the engine will run, but not the best. Common cause for code 8 is a damaged TDC from distributor bearing failure or open circuit in the sensor or wiring back to the ECU.



Basic Test


- Perform a Visual inspection and make sure the TDC sensor is Connected, listed for metallic sounds from the distributor. Save yourself allot of time, If you have a very noisy distributor with lots of grinding metallic sounds, replace your distributor.


TDC Sensor Pin out Picture

OBDO





OBDI




wire side of connector


( note, unfortunately TDC sensors come in a variety of different connectors for different types for Honda's. In this DIY, I have just covered the basic all in one distributor. If you have a 4 wire distributor, Legend ect, reply to this thread and I’m sure some one will be able to help. )


**** Resistance Test **** Set the multi meter to ohms ( 2k scale )


Unplug the TDC sensor, connect your Red multi meter lead to the TDCP. Connect your Black multi meter lead to the TDCG.


TDCP

OBDO = Pin 6
OBDI = Pin 3
OBDII = Pin 3

TDCG

OBDO = Pin 5
OBDI = Pin 4
OBDII = Pin 4

their are two types of sensors.

350ohm to 750ohm ( most Honda's are 350ohm to 750ohm)

or

700ohm to 1300 ohm


If your TDC is not with in spec replace it ( or the distributor ). To be safe, consult the workshop manual for the actual specs for you TDC.


**** Voltage Test ****


Set your multi meter to AC Volts ( 20v scale )

Step 1


Check the TDC sensor for its output Voltage to the ECU, Connect the Black Lead from your multi meter to the chassis for a good ground. Back probe* the TDCP ( Top Dead Centre Power) with the Red lead while the sensor is connected.


OBDO = Pin 6
OBDI = Pin 3
OBDII = Pin 3

KOER* at idle ( 800RPM ) you should get about 2vac
KOER* at 2500RPM you should get about 5.5vac



You can also test the TDC signal at the ECU connectors


OBDO = A11
OBDI = B13
OBDIIa = C3
OBDIIb = C20


If you do not get a signal, replace the TDC ( distributor )


**** Frequency Test ****


Set your multi meter to Hz scale


Step 1


Check the TDC sensor for its output frequency to the ECU, Connect the Black Lead from your multi meter to the chassis for a good ground. Back probe* the TDCP ( Top Dead Centre Power ) with the Red lead while the sensor is connected.

OBDO = Pin 6
OBDI = Pin 3
OBDII = Pin 3


KOER* at idle ( 800RPM ) you should get about .028khz
KOER* at 2500RPM you should get about .090khz


You can also test the TDC signal at the ECU connectors


OBDO = A11
OBDI = B13
OBDIIa = C3
OBDIIb = C20



If you do not get a signal, replace the TDC ( distributor )



**** Continuity Test ****




Set your multi meter to continuity. This setting is mostly a picture if a sound .))) when you touch the Red and Black leads together on your meter it should beep.


STEP 1

make sure the Ignition is off and unplug the TDC Connector and the ECU Connectors for this test

Continuity test between TDCP and ECU, Connect your Red multi meter lead on the TDCP, Back probe* the Black multi meter lead on the ECU Pin below that suits your car.




OBDO = A11
OBDI = B13
OBDIIa = C3
OBDIIb = C20




your multi meter should beep and read short or 000.0ohms. Place the black multi meter lead on a good ground source. You should not get beeping, this is testing for short to ground.



STEP 2

make sure the Ignition is off and unplug the TDC Connector and the ECU Connectors for this test

Continuity test between TDCG and ECU, Connect your Red multi meter lead on the TDCG, Back probe* the Black multi meter lead on the ECU Pin below that suits your car.




OBDO = A12
OBDI = B14
OBDIIa = C13
OBDIIb = C21




your multi meter should beep and read short or 000.0ohms. Place the black multi meter lead on a good ground source. You should not get beeping, this is testing for short to ground.






Advanced Test


You may pass all the above test with no problems at all. Unfortunately this does not mean all is well. You can have a sub code to the code.

example code 8 -1

code 4 is TDC

sub code 1 ( for example, ) is noisy TDC


You will not get sub codes from the SCS and MIL, you need the HDM or PGMFI Tester from the DLC port.

So in this advanced test, we are going to test the TDC with an Oscilloscope or Waveform Viewer to look at the signal generated from the TDC close up. The aim is to get a nice clean sine wave with out any glitches or drop outs.

Common causes of noisy sensors are rebuilt distributors. Once the bearing has failed and the pulsar has gone to town on the magnetic pickup and has damaged the pulsar and pickup assembly. Just changing the bearing in a dizzy rebuild sometimes doesn’t cut it. Also cracks in the sensor housing is a bad thing.

Test Time

Connect the Black Lead from your waveform viewer to the chassis for a good ground. Back probe* the TDCP ( Top Dead Centre Power) with the Red lead while the sensor is connected.


OBDO = Pin 6
OBDI = Pin 3
OBDII = Pin 3


KOER, you should get a pattern that looks abit like the pattern in the pic below.






you should not get a pattern with glitches or fuzz in the sine wave like in the pic bellow. if you do replace the sensor/distributor







* Notes

KOEO = Key On Engine Off

KOER = Key On Engine Running

Back probe the sensor, use a paperclip and push it into the connector then touch/clip your multi meter lead to the paper clip


Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!