How to Replace audi a4 spare key teaches you how to replace the G28 Engine Speed Sensor. This sensor is located on the outside of the transmission just above the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the location of the camshaft in order to 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 and possibly indicating the chain is stretched or a jump link on the upper timing chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky because there are two connector pins and they have different functions but the most effective way to test it is by measuring resistance between the sensor and the ECU. When the sensor is operational, it should read around 1000 ohms. audi a3 replacement key for signs of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors are not firing any more. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the 4th was dry. When I crank the engine without sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th stays shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero ohm. I assume that the problem is in another location.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.
I'm not sure what to do. I believe that I've eliminated everything else. However, i'm afraid that I might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. Test them out to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger an engine shutdown.
The signs of a failed G28 sensor are an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when you are in gear. If you have any of these issues it is likely your sensor is going bad and requires replacement. They are cheap and easy-to-find, especially if they're an Bosch unit like ours. You can also choose the GM version of this part is also a great option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for many issues in your car. It's a crucial component of the transmission in your Audi because it relays information to the ECU regarding how fast or slow the engine is spinning. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal to the ECU at pin T55/49 via an uncolored wire. The ECU uses this signal to regulate fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. You should observe around 1000 ohms of resistance between those two pins. This part is common across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU So, you may find them in wrecking yards.