AUDI EPC LIGHT
It is common knowledge that EPC light problems have been haunting Audi drivers incessantly for the past few years, announcing itself on Audi A1, Audi A2, Audi A3, Audi A4, Audi A5, Audi A6, Audi A7, Audi A8, Audi Q3, Audi Q5, Audi Q7, the Audi RS4, Audi RS6, Audi RS8, Audi R8, Audi S4, Audi S6, Audi S8 and Audi TTs even before they're run-in. Several Audi owners are dismayed that EPC problems present themselves on virtually new cars.
In fact, EPC problems pop-up at any time, on any Audi new or old fitted with X-by-Wire technology. Any Audi without a throttle cable, is naturally fitted with a full Drive-by-Wire system which is supervised by the Electronic Control Circuit (EPC) / Electronic Throttle Control (ETC) that turns on the dashboard mounted EPC (K132) indicator light when it detects a malfunction, then registers Diagnostic Trouble Codes (DTC) in the ECM memory. Even though the EPC light turns on exclusively for non-emission related faults, it does however turn on along with the MIL for emission related faults.
The EPC / ETC is a torque monitoring circuit and monitors for torque discrepancies and torque inefficiencies and when it detects one, sends the vehicle into emergency running mode (limp mode). These are prevalent when towing, when driving up an incline, when in manual mode, when in cruise control, after spirited driving, etc, and may even cause the ABS, ESP lights to came on. Some drivers, assume that it's happening more frequently over time and others are concerned that the EPC trouble are going to get worse because of its randomness. But this is not the case.
Bear in mind that once the EPC light is on, no other EPC related fault is going to make it glow any brighter. Once it's on, it's stays on even if the battery is disconnected, and it will come back on when you reconnect. However, the ECU will monitor the EPC circuit and if the same error does not occur in three successive trips of at least 7 kilometers, it will erase the DTC and it would seem as if it never happened, until the next time. These are safely features specific to Drive by Wire systems and their workings can be viewed in the adaptation groups when retrieving errors with a scan tool.
ADAPTATION GROUPS PERTAINING TO EPC
Group 60 -- Throttle Valve Adjuster / Adaptation Epc-system
Group 61 -- Epc-system / Throttle Valve Adjuster (System 1)
Group 62 -- Epc-system / Throttle Valve Adjuster (System 2)
Group 63 -- Kickdown Function
Group 66 -- Cruise Control Status
AUDI EPC LIGHT RELATED DTC
18039 / P1631 - Accelerator Position Sensor (G79): Signal too High
18041 / P1633 - Accelerator Position Sensor 2 (G185) Signal too Low
18042 / P1634 - Accelerator Position Sensor 2 (G185): Signal too High
18047 / P1639 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal
00777 - Accelerator Position Sensor (G79): Implausible Signal
No response from the throttle even with your foot flat on the accelerator pedal.. There are two potentiometers fitted to the accelerator pedal which are monitored by the ECU and when it it detects an intermittent signal from one pot, it turns on the EPC light then uses the second pot for acceleration but it is limited. When both pots detected as are intermittent, EPC light goes on and engine only runs at idle speed. When this error occurs, turn the engine off, stomp on the accelerator a few times through its full travel. It could just be specks of dust that settled on the one of the potentiometer (variable resistors) tracks that stymied the ECU for a few millisecond or so. I this happens often and thereafter, presenting a 18047 / P1639 or 18039 / P1631 or 18042 / P1634 or 18041 / P1633 then consider replacing the accelerator pedal.
No response from the throttle even with your foot flat on the accelerator pedal. There are also two redundant potentiometers in the throttle body that determines the throttle valve angle and it has three modes of failure. One for when the valve angle sensor fails, one for when throttle valve actuator (motor) malfunctions and one for when throttle valve position is cannot be recognized by the ECU. When this happens the ECU shuts off the voltage supply to the actuator, causing the throttle valve to defaults to mechanical stop position and the engine speed is limited to 1200 RPM. If any of the DTC fault below show up in your scan, check the 6 pin plug interfacing with the throttle body. It would be best to redo adaptation thereafter before thinking of replacing the throttle body.
000289 / P0121- Throttle Position Sensor (G69): Implausible Signal - Intermittent
16506 / P0122 - Throttle Position Sensor (G69): Signal too Low - Intermittent
17987 / P1579 - Throttle Actuator (J338): Adaptation Not Started - Intermittent
17976 / P1568 - Throttle Actuator (J338): Mechanical Failure
17972 / P1564 - Throttle Actuator (J338): Under-Voltage during Basic Setting
17952 / P1544 - Angle Sensor 1 for Throttle Actuator (G187): Signal too Large - Intermittent
16606 / P0222 - Angle Sensor 2 for Throttle (G188): Signal Too Low - Intermittent
000547 / P0223 - Angle Sensor 2 for Throttle (G188):Signal Too High - Intermittent
17581 / P1173 - Angle Sensor 2 for Throttle Actuator (G188) Signal too High
18042 / P1634 - Accelerator Position Sensor 2 (G185): Signal too High
You have difficulty starting but eventually does start but idles very rough, bucks and surges when you attempt to drive it. The EPC, MIL (Check engine light) and ESP lights come on. This is most likely caused by the Injectors N30-N33 or the Ignition Coils N (1st cylinder), N128 (2nd cylinder), N158 (3rd cylinder) and N163 (4th cylinder) since both the Injectors and Ignition coils causes exactly the same symptoms. It also exhibit the following DTCs.
17633 / P1225 - Fuel Injector for Cylinder 1 (N30): Short to Ground - - Intermittent
17634 / P1226 - Fuel Injector for Cylinder 2 (N31): Short to Ground - - Intermittent
17635 / P1227 - Fuel Injector for Cylinder 3 (N32): Short to Ground - - Intermittent
17636 / P1228 - Fuel Injector for Cylinder 4 (N33): Short to Ground - - Intermittent
MORE EPC PROBLEMS
J757 Engine Component Power Supply Relay cause loss of high-pressure and turns on EPC. ESP and MIL lights.
N75 Solenoid valve for charge pressure limitation and turns on the EPC and MIL lights but shown no symptoms of failure except go into limp mode.
Audi A1, Audi A2, Audi A3, Audi A4, Audi A5, Audi A6, Audi A7, Audi A8, Audi Q3, Audi Q5, Audi Q7, the Audi RS4, Audi RS6, Audi RS8, Audi R8, Audi S4, Audi S6, Audi S8 and Audi TTs EPC Problems.
I have one. 2010 a4 b8. usually at running temp, and approx. 750 to 1200 rpm, when I go to accelerate normally, I get the epc light, a stumble, and maybe a die situation. the epc can be duplicated. the die is sporadic.when the die occurs it gives a p0341 code. any help would be great. I have done the n205, g40, and oil pan pickup solenoid with no fix. I found it may be the crank sensor, g28? if I do keep the rpms over 1k, it never stumbles, and no epc light. many thx
ReplyDeleteHi Mark
DeleteDTC P0341 / VAG NO 16725 on an Audi a4 b8 is related to the camshaft position sensor A (G40), that's sending an implausible signal. Implying that the ECU don't know how to interpret it. Since you already replaced bank 1 camshaft adjustment N205 as well as g40, it could perhaps be the other two sensor. Bank 2 camshaft adjustment N208 valve and camshaft position sensor A Bank-2 (G163), either or both giving implausible signals. Just wondering if you cleared the DTC memory after you replaced N205 and G40. If you didn't the ECU is still under the impression that they are faulty.
However, if the crank position sensor g28 is faulty, the car will start for a brief second then switch off again, the engine will not keep running. Seeing that the engine runs steady under 1000 rpm it can't be G28.
Having said that, if the EPC light comes on, its related to the (Drive-by-Wire) throttle valve actuator adjustment / Idling Control / Adaptation of the Electronic throttle body - EPC-System.
As a result the voltage to the actuator is shutoff and the throttle valve returns to its defaults mechanical position - (stop position), limiting the engine speed to about 1200 RPM. Check the values in display group=60, display group=61 and display group=62 (EPC- system) this may help.
assuming n208 is in the oil pan, the pickup as the shop called it. where is g163? and yes, cleared the ecu. are there any normal parts that go bad on the drive by wire system I can try, before having to do the dealer again? they seem lost. it does seem to do this only when the engine is at running normal temp, no other time. if that helps. g40 has been changed twice now, so g163 maybe?
ReplyDeleteHi Mark
ReplyDeleteThe intake Variable Valve Timing Actuator / Camshaft Adjustment Valves are N205, N208 and N318, N319 are the exhaust Camshaft Adjustment Valves. Remove these valves and check the solenoids for continuity, they should measure between 10 and 20 ohms, If resistance is OK, check for +B ((12V) supply. It could be the fuse to the solenoid that's blown. Bear in mind the timing control only kicks in about half a minute after the engine is started and only then transmits oil pressure to the mechanical camshaft adjuster as needed. These solenoids are situated near the top of the engine and the engine heat can destroy the wiring to the solenoids. Check if the wires aren't open circuit. The fact that you say is only happens when you accelerate, it could even be your accelerator pedal senders. However, the P0341 fault says that the solenoid are not doing what they supposed to do.
Hi, thank you for this information. I have just bought a 2017 Audi S1 with only 400km. It is a few years old so has been sitting around no doubt at the dealer. Today after filling with fuel the epc light came on when J restarted the car. There was no impact at all to driving performance. I pulled over after a few minutes and then turned the car off and then back on. The light has not come back. I will take to a dealer to see if any fault codes are present, but I am curious if you have any ideas what this could mean? Car drives perfectly so not sure why the light came on? Thanks
ReplyDeleteno idea. mine now has an issue when leaving work, after 5 miles or so, rpms jump around, and then may die or get an epc light. doesn't do it on the morning drive. no codes and after a restart it never reappears. i have a stage 1 tune, so the epc removes this performance, i can tell. till stumped. like i said, a restart after the 5 miles item, it never comes back.
ReplyDelete