What Does P0946 Mean?
DTC P0946 indicates the hydraulic pump relay circuit is operating outside its expected performance range. The TCM detects that the relay is switching but not performing correctly, such as excessive voltage drop across the relay contacts, slow actuation, or inconsistent pump motor engagement. This code suggests the relay or its circuit is degraded but not completely failed.
Common Causes
30%
Hydraulic pump relay with worn or pitted contacts causing high resistance
25%
High-resistance connections in the relay circuit wiring
20%
Corroded relay socket terminals causing voltage drop
15%
Hydraulic pump motor drawing excessive current (worn brushes, bearing failure)
10%
Weak relay coil causing intermittent or incomplete contact closure
Diagnostic Steps
1
Step 1: Measure voltage drop across the relay contacts while the pump is running. With the pump motor drawing normal current, voltage drop should be less than 0.5V. Higher readings indicate worn contacts.
2
Step 2: Check the relay socket terminals for corrosion, heat discoloration, or signs of arcing. Clean or replace the socket if damaged.
3
Step 3: Measure the pump motor current draw during operation. Excessive current (significantly above specification) indicates a failing motor that is overloading the relay.
4
Step 4: Inspect all wiring connections in the pump relay circuit, including ground connections, for high-resistance joints. Repair or replace any degraded connections.
5
Step 5: Replace the relay with a new OEM-specification relay. If the code returns, investigate the pump motor itself as the root cause of relay degradation.
Estimated Repair Cost
$80 - $450
Parts + labor, varies by vehicle and location
DTC P0946 indicates the hydraulic pump relay circuit is operating outside its expected performance range. The TCM detects that the relay is switching but not performing correctly, such as excessive voltage drop across the relay contacts, slow actuation, or inconsistent pump motor engagement. This co...
The most common cause of P0946 (Hydraulic Pump Relay Circuit Range/Performance) is: Hydraulic pump relay with worn or pitted contacts causing high resistance
Typical repair costs for P0946 range from $80 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A degraded relay circuit may cause sluggish pump operation, resulting in slower pressure buildup and delayed shifts. If the relay degrades further, complete pump failure could occur, leading to loss of transmission function. Prompt relay replacement is recommended.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0946 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Clutch Hydraulic System
Difficulty
Type
Generic (SAE)
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