Diagnostic Results

Results friend 1 4A-G 20v AFM

November / December 2003

Upon checking the ECU's error log, known as D.T.C. The results came out

"Communication Error" Please perform...... bla bla bla, Please see ..... bla bla bla etc etc etc.

This is because the wiring loom is cut and join with the old wiring loom. This is not the real problem, the real problem is during integration of the new wiring to the old wiring, some wires are connected wrongly and / or incomplete.

It is extremely sad and surprise to find this result because the transplant it perform in a known good workshop.

Injector Pulse Width 2.x ms  
Ignition Advance 9 CA  
ISC duty 3x %  
Engine Speed 750 rpm  
Air Flow 3.8 v  
Coolant temperature 8x c  
Throttle Position 0 %  
Vehicle Speed 0 kmh  
Target A/F Left ? v  
A/F Feedback Left OFF    
Knock Feedback OFF    
Starter Signal OFF    
Idle  ?    
A/C Signal OFF    
O2 feedback ?    

The most surprising issue is that AFM voltage is 3.8v. This means the ECU thinks it opens very little, which is good for fuel economy. (Theoretically)

Another surprising issue is that IDLE signal cannot be ON of OFF accordingly.

What happen is that the TPS adjustment is not in SYNCRONISATION with the IDLE output signal.

The correct result is TPS at 0% and the IDLE signal will output ON, so that the ECU will think the engine is not moving and goes into fuel economy mode and engage exhaust sensor heater in hope to maintain accuracy, and perhaps will still read exhaust signal as "suspect".

Other ancillaries will follow suite, the air-cond system will know there is no speed hence no free flowing wind hence have to push the fans harder and longer. Etc etc etc.

EFI, aren't it a great thing

Anyway, the TPS should not be -0% (minus) as the diagnosis reader is unable to display negative values. This is why it needs to be tested properly as stated in Diagnostic by DCN Pro Hand Part 2.

The test is very simple and consists of: -

  1. TPS at 0%
  2. IDLE says ON
  3. disturb the throttle very quickly and momentarily then release and observe how sensitive it is.
  4. If upon small disturbance and the IDLE says OFF means it is very good.
  5. If upon small or heavy disturbance but still no change then it could be either the TPS is old and insensitive??? or that the TPS has been retarded into the negative range.
  6. Therefore release the TPS and push into the 1% and IDLE OFF state
  7. Then slowly and lightly knock it back to TPS 0% and IDLE ON.
  8. Try 3 again until successful.

If fail, then something is wrong.

In this case the TPS went up to 8%, but IDLE still says ON, which is obviously wrong.

The calibration between TPS and IDLE signal is extremely important because: -

  1. If TPS is -5% then the user always have to pedal harder to get some form of an effect from the engine.
  2. When there is TPS signal above 0% but IDLE remains ON, then the ECU will think that the car is not moving hence always stay in fuel economy mode.
  3. Not only that, the ECU will also NOT advance the ignition timing and hence the user pedals allot but engine is reluctant to increase RPM easily.
  4. When engine rev beyond the 0% TPS and IDLE signal become OFF then suddenly the ECU advance timing, delivers more fuel and the engine suddenly feels very powerful.

This are all not correct ECU and engine operations.


  1. Diagnosis System
  2. Diagnostic by DCN Pro
  3. Diagnostic for a friend
  4. Different Diagnosis
  5. Results 1
  6. Results 2
  7. Results 3
  8. Results 4
  9. References



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