P0946

Hydraulic Pump Relay Circuit Range/Performance

Severity: High
Driving: Drive only to a garage

The hydraulic pump relay circuit is electrically sound but the relay is not behaving as commanded - slow to switch, sticking, or not releasing. Usually the contacts are worn, which is a mechanical failure inside the relay rather than a wiring problem.

Possible causes

CommonRelay contacts worn, sticking or welded
CommonCorroded relay socket adding resistance
CommonWater ingress into the fuse box
PossibleWeak battery making relay operation marginal
PossibleHigh resistance in the control wiring

What you might notice

Pump running when it should not, or not running when it should
Battery draining after standing
Slow or failed gear changes
Transmission warning message

What to check, in order

Swap the relay first. Worn contacts are the most common cause and swapping confirms it immediately.
Inspect the socket for corrosion and heat damage.
Check battery voltage - a weak battery makes a marginal relay behave exactly like a failing one.
Check the fuse box for water.
If the battery drains overnight, a relay that will not release is a likely cause and worth investigating rather than dismissing.

Read this code from your own car

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Where this code sits

B · Body C · Chassis P · Powertrain U · Network and communication

Transmission and control modules