How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge just above the flywheel gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control fuel and boost. 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 must know when the crankshaft reached TDC, and the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
how much is an audi key replacement is a bit challenging as there are two different pins for the connector and they serve different purposes but the best way to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should be reading around 1000 ohms. Look for evidence 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 full speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or my injectors weren't firing. This morning i pull out the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I crank the engine without sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stays shut. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However, the intermittent misfire problem continues to occur 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 when I crank up the engine.
audi tt keys 'm not certain what to do, but i believe that i've ruled out everything else. But i'm worried that I might have missed something. Let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sender is identical to the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. Test them out to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black end of the connector). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must know the speed and position of the crankshaft to make decisions about timing of the fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will show codes that could cause an engine shutdown.
Some of the signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when you are in gear. If you have any of these issues, it is likely that your sensor is deteriorating and should be replaced. They're cheap and easy to find especially when they're an Bosch sensor like ours. Alternatively, the GM version of this component is also a great option.
5. Tachometer
A faulty engine speed sensor could be the cause of a slew of problems in your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU regarding how fast or slow the car's engine is turning. If this sensor fails, it could disrupt the performance of the transmission and the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU is then able to process the signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located 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 [79]), and between pin T6a/1 and pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a common part across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.