Checking continued coolant circulation relay J151: Audi 4.2 (BCY, BRV)
Step-by-step checking continued coolant circulation relay J151 for the Audi 4.2 (BCY/BRV): factory workshop text.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
📐 4 workshop diagrams for BCY
Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.
📋 Procedure
Checking
continued coolant circulation relay
J151
Special tools and workshop equipment required
Hand-held multimeter
V.A.G 1526C
Auxiliary measuring set
V.A.G 1594C
Test sequence
Note
Function
Chapter
Continued coolant circulation pump
V51
checked
Chapter
, result of check
“voltage supply n. OK”
Coolant temperature when switching off engine must be at least 60 °C; this ensures that the continued coolant circulation pump actually starts up.
Switch off ignition.
Note
The test must be carried out within 15 minutes after switching off ignition.
Detach rubber seal from plenum chamber cover in direction of
arrow
.
Detach plenum chamber cover
1
towards the front.
Remove cover for electronics box in plenum chamber
arrows
.
Unplug
continued coolant circulation relay
J151
from position
2
.
Checking earth supply of
continued coolant circulation relay
J151
Connect multimeter (voltage measurement range) as follows:
3-position relay carrier in electronics box in plenum chamber, position 2
Contact
Measure against
2
Battery positive
Specification: approx. battery voltage
If specification is not obtained:
Repair open circuit or short circuit in wiring (refer to current flow diagram).
If specification is obtained:
Checking voltage supply of
Motronic current supply relay
J271
Note
The positive supply to the
continued coolant circulation relay
J151
comes from the
Motronic current supply relay
J271
. The voltage supply is maintained for at least 15 minutes after the ignition is switched off.
Connect multimeter (voltage measurement range) as follows:
3-position relay carrier in electronics box in plenum chamber, position 2
Contact
Measure against
3
Engine earth
Specification: approx. battery voltage
If specification is not obtained:
Perform the following checks marked with a dot.
Check fuse S78 in electronics box in plenum chamber (socket not specified).
Use current flow diagram to check for open circuit in wiring from
continued coolant circulation relay
J151
(in 3-position relay carrier in plenum chamber electronics box) to
Motronic current supply relay
J271
.
Check
Motronic current supply relay
J271
Rep. Gr.
24
.
Checking actuation from alternator terminal 61
Note
The earth supply to
continued coolant circulation relay
J151
comes from alternator terminal 61 (with the engine stopped).
Connect multimeter (voltage measurement range) as follows:
3-position relay carrier in electronics box in plenum chamber, position 2
Contact
Measure against
1
Battery positive
Specification: approx. battery voltage
Start engine.
Specification: approx. 0 V
If specification is not obtained:
Check wiring from
continued coolant circulation relay
J151
to alternator terminal 61 for open circuit.
If no fault is found:
Renew
continued coolant circulation relay
J151
.
TorqFix answers live for your specific car — tell it the engine code and it serves the matching sequence, torque figures and wiring for that exact variant.
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
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The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.