How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft reached TDC, and where the camshaft lies to trigger the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. car key replacement audi indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult because there are two pins for the connector and they have different functions however the best method of testing it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when it is operating at its maximum. If you're having issues with this component, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive decrease in power. It was as if the engine was running out of gas. Or my injectors weren't firing. This morning i pull out the spark plugs, 3 were drenched in gazoline, the fourth one was dry. When I start the engine, there are no sparks, I put a piece of tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I'm assuming the issue is in another place.
I also tried to reset the PID without success. The car can start if the G28 is disconnected and runs fine when it is plugged in but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows a temperature of -49c. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I believe that I've ruled everything else out. I'm worried that i might have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or from a parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that must know the speed and position of the crankshaft in order to make decisions about fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either one of these, the diagnostic scanner will display codes that could cause the engine shutting down.
A damaged G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or a misfire in gear. It is possible that the sensor is failing and requires to be replaced if you encounter any of these symptoms. They're cheap and easy to find particularly in the case of an Bosch unit like ours. Alternatively, GM's version of this part is an option.
5. Tachometer
A failing engine speed sensor could be the reason behind many issues in your vehicle. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. The ECU is then able to process this signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is a common part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.