0103 - Checking the electronic idle speed control (note deviations for off-road vehicles) Engines 601, 602.91, 603.91

07.1-103 Checking electronic idle speed control

Engines without test coupling (X92)
(Engines with test coupling (X92) see 07.1-105 Checking ARA and/or ELR).

Test and adjusting values

1) Automatic transmission
2) Manual transmission

Special tools

Commercially available tools

Note
Electrical wiring diagrams see

job no. 07.1-400.

Testing jobs

-------------------------------

Connect digital tester (001) and pulse
generator (021).

Check control for easy operation and condition.

Check idle speed stop on Bowden cable (230).

The spring retainer (226) of the Bowden cable (230) in idle speed position must contact the compression spring (227) without preload.

Run engine to 60-80 °C coolant temperature.

Checking overvoltage protection (K1 or K1/1)

Switch on ignition, pull off control unit (N8 or N8/1) and check voltage between the jacks (9 and 11).

Display: approx. = 12 V

No

Yes

Check fuse on overvoltage protection. Check activation according to electrical wiring diagram.

End of test

Function check

Engine idling. Pull double coupling (arrow) off ELR electromagnetic actuator (Y22) for at least 3 s and refit. Engine speed increases briefly.

Yes

No

Briefly apply battery voltage (approx. 12 V) to ELR electromagnetic actuator (Y22). Idle speed increases.
Caution!
If battery voltage is applied for longer than 3 s the ELR electromagnetic actuator will be damaged.

Yes

No

Renew electromagnetic actuator (Y22).

Check individual parts.

Engine idling. Pull double coupling of electromagnetic actuator (Y22).
Check idle speed.

Set values:
Engine Idle speed/min

601.91 66040

602.91 62040

603.912+603.913

with automatic transmission 58040

603.913

with manual transmission 62040

Yes

No

End of test

Adjust idle speed by loosening lock nut (arrow).

left = higher
right = lower

End of test

Checking speed sensor (L3)

Renew starter ring gear speed
sensor (L3).

Engine switched off. Remove plug connector (L3x). Connect multimeter and press key "W". Check resistance.

Yes

No

Display: 0.4-2.5 kW

Inspect starter ring gear speed sensor for accumulation of dirt or metal chips, clean if required.

Multimeter connection as above, press key
"V". Run engine at idle speed.

End of test

Yes

No

Display: > 4 V AC
Voltage rises with speed.

Checking coolant temperature sensor (B11/1)

Engine switched off. Remove plug from temperature sensor and measure resistance against ground.
Set values see diagram.
Measure resistance at two temperature measuring points.

Example:

+20 °C = 2.2-2.8 kW

+80 °C = 290-370 W

No

Yes

Renew coolant temperature sensor.

End of test

Measure voltage on 1-pole coupling (arrow) "Ignition" On.

Display: approx. 5 V

End of test

Eliminate line interruption. Renew control unit (N8 or N8/1).

No

Yes

Checking electrical activation of electromagnetic actuator

Engine idling. Remove double coupling (arrow) from electromagnetic actuator (Y22) and measure voltage with multimeter in key "V =".

Display: approx. = 12 V

End of test

Check activation according to electrical wiring diagram, renew control unit (N8 or N8/1) if required.

No

Yes