Motor Speed Sensor & Control Unit Failure

Car: Volkswagen Golf 5 Variant, 1.9 TDI, 105 hp, 2008, mileage 187,000 km.

While overtaking on the highway at 80 km/h in heavy rain, the Golf's engine shut off and could not be restarted. The ADAC (German automobile club) had to tow the car to a workshop. The workshop checked the wiring to the G28 sensor and then offered to replace the sensor and rewire the cables for 500 euros.

I haven't had anything done yet because, for me, it's either a sensor signal or it's not. If G28 were defective, the engine wouldn't start.
Cables were only inspected in the visible area. The oil filter housing and its connection to connector G28 have not yet been disassembled.

Auto springt in Trockener Werkstatt wieder an und läuft jetzt wieder. Ersten Code Glühkerze ist bei altem km Stand. Fehler codes:

3 error codes found:
005660 - Spark plug, cylinder 3 (Q12)
P161C - 000 - Interruption.
Environmental conditions:
Error status: 01100000
Error priority: 3
Error frequency: 1.
Lost Count: 255
Mileage: 172,783 km
Time: 0.
Date: 2000.00.00
Time: 07:08:19

Environmental conditions:
Speed: 819 RPM
Speed: 0.0 km/h
Last: 0.0%
Voltage: 14.06 V
Binary value: 00000100
Temperature: 14.4°C
Binary value: 10110000

000801 - Sensor for motor speed (G28).
P0321 - 000 - Implausible signal - Intermittent.
Environmental conditions:
Error status: 00110000
Error priority: 1.
Error frequency: 1.
Lost Count: 255
Mileage: 187,233 km
Time: 0.
Date: 2000.00.00
Time: 07:57:18

Environmental conditions:
Speed: 1764 RPM
Speed: 68.0 km/h
Last: 35.3%
Voltage: 14.29 V
Binary value: 00000100
Idle stabilization: 0.0° KW.
Speed: 1323 RPM

001542 - Control unit defective.
P0606 - 000 - CPU failure - Intermittent.
Environmental conditions:
Error status: 00100000
Error priority: 2
Error frequency: 1.
Lost Count: 255
Mileage: 187,233 km
Time: 0.
Date: 2000.00.00
Time: 07:57:48

Environmental conditions:
Speed: 5334 RPM
Speed: 71.0 km/h
Last: 0.0%
Voltage: 14.36 V
Binary value: 00000100
Hex Value: 0xFF00
Torque: 0.0 Nm

Readiness: 0 0 0 0 0

Hello,

Since the issues with the sensor and the control unit occurred simultaneously, you should definitely check the wiring harness leading to the engine control unit for any defects. Also, make sure the engine control unit is dry and doesn't end up submerged in water during rain.

Best regards, Rainer.

Thanks for the heads-up. I'll check it out over the weekend and get back to you.

The engine control unit was checked today. No abnormalities were found in the wiring, and the connectors are dry. The connectors were disconnected and inspected internally. They are in like-new condition. The next step is to remove the oil filter housing and check the connectors directly connected to the G28 sensor. I will replace the G28 sensor at the same time.

Today, with dry weather, I had no problems on an 80km highway drive.

Hello,

It might also be worth checking the larger fuses. I once had a situation with an A3 8L where a corroded fuse holder on the battery caused problems with the engine control unit (resulting in malfunctions in the vehicle's electrical system).

Best regards, Rainer.

Hello, error found!

There was another error in the Autoscan:

Address: 08 Climate/Heating Department.

00898 - Control of air conditioning compressor. 010 - Open circuit/short circuit after positive terminal.


I then checked the connectors and found a loose connection at the air conditioning compressor.
This connector is located directly behind the engine fan, so moisture can easily get to the contacts when it's wet.

Thank you for the helpful tips in troubleshooting.

Hello,

The loose connection may potentially cause other errors, but I'm not entirely sure that everything is now okay.

Water doesn't cause short circuits at 12V.

Best regards, Rainer.

Update: It wasn't the climate control connector as initially suspected, but rather the contacts on the connector directly connected to the sensor. Since the car has been running perfectly since being towed from the workshop until today, I haven't contacted the workshop again.

The mechanic did more work than I was informed about. Specifically, while disconnecting the connector for the engine speed sensor (G28), he damaged the connector on the wiring harness side. This connector was replaced, and the contacts of both connectors were cleaned. According to the mechanic, the connector was likely already faulty, and over time, dirt and oil had accumulated on the contacts, causing the connection to deteriorate until it eventually failed. This explanation seems very plausible as the main cause.

I will continue driving without replacing the sensor, because if there were no previous issues, the likelihood is high that the problem has been resolved by cleaning and replacing the connector housing.

Thank you for the feedback .