Speedometer went down to 0 while driving, D4 light flashing

Alex, thank you so much! I have been searching online about the DLC code, but this is the only clear and complete documentation about the system. According to your instructions, the Check Engine light should be flashing when shorting the Service Check connector. However in my case, only the D4 light was flashing. Did they mean the same? Now I am sure the numbers I got were 4, 15, which according to your list, mean Crankshaft Position CKP sensor and Ignition Output Signal respectively. Could you give me a little bit of explanation?

That's wonderful! I really appreciate the information you provided. I am going to do my home work and get back to you in a couple days.
Thanks

Godwin

Hi Alex,

Something happened on Friday and Saturday. My car used to stall only at low speed. But on Friday, I was driving on a freeway around 60m/h, my car suddenly lost power completely and slowed down. Stepping on the gas pedal had no help. But it’s strange that the engine was still running around 2000 rpm. A few seconds later the engine died. I pushed the transmission to the neutral position and restarted the car. It then worked fine afterward.
On Saturday, Same thing happened again on a freeway. But I wasn’t that lucky. The car kept stalling every few minutes for around 5 to 6 times. So I ended up towing the car home. I checked the DTC code again. It was still the 4 and 15 with D4 flashing.

Today, I spent a whole day studying the documentation you gave me, searching Google and following the procedures to test my car. I mainly focus on the transmission DTC code since only the D4 was flashing. I managed to find the Main shaft Speed Sensor, the TCM and did all the tests.

On the Transmission DTC code 4 troubleshooting, I reached the last step: Check for loose TCM connector or substitute a good TCM and recheck.

On the Transmission DTC code 15 troubleshooting, I reached the step that reconnecting the Mainshaft Speed Sensor and measure the resistance between D19 and D12. The resistance was 400-600 Ohm, and the conclusion was to run Electrical Troubleshooting for code 9; Check for loose TCM connector or substitute a good TCM and recheck.

It seemed to me that both main shaft speed sensor and vehicle speed sensor were OK. What should I do next?

My car was able to drive again today but I felt unsafe to drive it because the problem could come back anytime in any situation.

Thank you so much for your help!

Godwin

Hi Alex,
Did you include diagrams? I don't see them.
Thanks,
Godwin

I got the instructions, thank you so much! If I buy a new or a used TCM, do I need to do any configuration or any preparation before replacing the existing one?
Thanks

Godwin

Last week, I found some videos on YouTube suggesting a faulty main relay might be the reason for the engine random stalling problem. I pulled out the main relay and did find cracks on a couple of solder joints on the PCB inside the relay. I fixed it myself because I am very good at electronics. I also replaced the Vehicle Speed Sensor because the speedometer dropped to 0 multiple times while I was driving. Since then, I have been driving my car for 4 days. So far so good, don’t have any problem.
But I don’t know how to clear the DTC codes. I pulled out the fuse for the ECU inside the fuse box under the steering wheel. But the codes are still there. Do I have to disconnect the battery terminal?

Yes, I disconnected the battery negative terminal for 5 minutes and reconnected it back. I then shorted the service connector and turned the ignition key on to check the code. The D4 light was off but the Check Engine light was steady on and didn’t go away. Well, before I disconnected the battery cable, the Check Engine light flashed the code 17, indicating the VSS problem. That’s why I replaced the VSS last week. But now the Check Engine light is steady on without flashing any code. What does it mean?

Hi Alex,
Thank you for the troubleshooting diagrams. I downloaded and saved them.

I got the D4 flashing code 4 before, which is VSS problem. I went through the troubleshooting procedure you gave me but didn’t find anything wrong with the sensor. Your recommendation earlier was to replace a new TCM. I later got the Check Engine Code 17 which was similar to the D4 code 4. Since this was an intermittent problem, I decided to replace the vehicle speed sensor first because it’s cheaper than replacing the TCM. My car has been running for a week without any problem since then.

Now the only issue is, the Check Engine Light was steady on when shorting the Service Connector. I disconnected the battery to reset the TCM and ECM. But the Check Engine light became steady on, and was not flashing any code. What did it mean?

Hi Alex,
Sorry I didn't respond earlier due to the corona-virus issue. I think the procedure you posted last week was not really related to my situation. First, the MIL won't come in normal operation. It only lights up when I plug the jumper into the service connector. It was steady on, no blinking. (The D4 light never come on again after I fixed the main relay and replaced the VSS). Second, I did remove the battery negative terminal for more then 10 minutes. Since then, my car has been driven for more that two weeks. But it still didn't clear the MIL. Does it indicate anything wrong?

Thanks

Hi Alex,

Thank you again for being so helpful, much appreciated.

Godwin