How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC and also the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper timing chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky as there are two different connector pins, and they perform different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. Examine for signs of coolant or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a massive reduction in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs, 3 were drenched with gazoline the 4th one was dry. When i crank the engine without sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th stay shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero ohm. So i assume the problem is in another place.
I also tried more info to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. I more info also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not certain what to do, but i believe that i've completely ruled out all other lost audi key possibilities. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel lost audi key Pump
The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. It is easy to test them - simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft in order to make a decision about fuel injector timing, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will display the codes that could trigger an engine shutdown.
Some of the signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal and/or a misfire when in gear. It is likely that the sensor is failing and needs to be replaced if you encounter any of these symptoms. They're cheap and easy to find especially in the case of an Bosch unit like ours. If you prefer, GM's version of this component is an option.
5. Tachometer
A damaged engine sensor could cause a myriad of issues within your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. When this sensor fails, it can cause problems for the transmission as well as the rest of the car's components.
The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU then uses and processes this signal to regulate fuel, timig and boost, and also sends it on to the G5 Tachometer located in the what is the audi advanced key instrument cluster. You can test for sensor failure by checking continuity from 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 [79]), and between pin T6a/1 and pin T26a/12. There should be an average resistance of 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU, so you might find good ones in wrecking yards.