K6JRF at the mic K6JRF's Page
formerly W6FZC


My Mercedes Benz
S500 Coupe

K6JRF's MB S500 Cpe
(Updated: Mar 2, 2007)

Analyze and Troubleshoot "Check Engine" MIL and Electronic Control Units (ECU)!

Electronic Accelerator/Cruise Control/Idle Speed Control N4/1

Description and Operation
The electronic accelerator control (EA) module (N4/1) controls the cruise control, idle speed functions and electronic engine control (electronic accelerator pedal) for ABS/ASR to ensure smooth and consistent operation regardless of engine temperature and load. The module is located in the module box, F23 and is color coded ORANGE.

AST Pointer Scan Tool & Mushroom Adpater When the ignition switch is in the ON position, the idle speed control function is in operation. The position of the throttle valve for idle speed and ABS/ASR is determined by this module via the nominal value of the accelerator pedal input potentiometer in the electronic accelerator actuator M16/1. The actual value of the potentiometer signals the position of the throttle valve. The EA module compares the signals and specifies the position of the throttle valve via the output signal. This signal is used by the electronic accelerator actuator to adjust the valve.

Before starting the engine, the throttle valve position is determined by the engine temperature. Once the engine is running, the idle speed and ABS/ASR are controlled by the EA module which provides a constant idle RPM and limits the maximum torque output to the drive wheels. For torque output regulation via ABS/ASR, the control module uses the input signal from the ABS/ASR control module.

The EA module uses the following information to determine the throttle position:
- Base module (N16/1)
- ABS/ASR control module (N30/1)
- LH-SFI control module (N3/1)
- Idle speed contact switch (S29/3)
- Electronic accelerator actuator (M16/1 with throttle valve)
- Stop lamp switch (S9/1)
- Started lockout/backup lamp switch, selector lever position recognition (S16/3)
- Cruise control switch (S40)
- A/C compressor engagement signal
- Data exchange via controller area network (CAN)
- Wheel speed sensors (L6/1 - L6/4)
- Diode matrix (V2)

Output signals:
- Electronic accelerator actuator (M16/1 with throttle valve)
- ABS/ASR control module (N30/1)
- LH-SFI control module (N3/1)
- EZL/AKR ignition control module (N1/3)
- Impulse readout to malfunction memory via 38 pin diagnostic connector (X11/4)
- Data exchange via controller area network (CAN)

The idle speed control function uses the following information to determine the correct idle speed:
- Engine speed (TN signal)
- Coolant temperature
- Vehicle speed signal
- Selector lever position
- A/C compressor engagement signal
During idle, the control module keeps the engine speed at a constant RPM depending on engine coolant temperature.

The warm-up control is effective at all engine temperatures. After each start-up (accelerator pedal in idle position), the engine increases the idle speed for appox. 20 seconds. Between 68 deg F and 86 deg F, the engine speed is 800 - 900 RPM.

When the A/C compressor is turned on, the throttle valve opening is increased just before the A/C compressor engages. This compensates for the A/C compressor load and keeps the engine idle speed at a nearly constant RPM.


Fault Table, DTC Readout, EA/CC/ISC Module (N4/1)

Socket 1: Black (Ground)
Socket 3: Red (+12.5V)
Socket 7: Yellow (Pin for EA/CC/ISC DTC readout)

DTC Readout Possible Cause
1 No Faults in System
2 EA/CC/ISC control module (N4/1) or safety contact switch (M16/1s1) or Stop Lamp switch or Cruise control switch or Actual value potentiometer or Starter lock-out/back-up lamp switch (S16/3) or Engine speed signal or Vehicle speed signal or Closed throttle position switch or Safety relay in EA/CC/ISC control module
3 EA/CC/ISC actuator (M16/1)
4 Cruise Control switch (S40)
5 Stop Lamp switch (S9/1)
6 Starter lock-out/backup lamp switch (S16/3)
7 Data bus (CAN):
msg from EA/CC/ISC control module (N4/1) faulty
msg from LH-SFI control module (N3/1) faulty
msg from Ignition Control module (N1/3) faulty
8 Left front axle vehicle speed sensor (L6/1) from ABS/ASR control module (N30/1)
9 Left rear axle vehicle speed sensor (L6/3) from ABS/ASR control module (N30/1)
10 Engine speed signal (TNA) from Base Module (N16/1)
11 Fuel safety shut-off to LH-SFI control module
12 EA/CC/ISC module voltage supply, circuit 87
13 Not used
14 Closed throttle position contact switch (S29/3)
15 Data exchange with ABS/ASR control module (N30/1) inoperative

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