What Does P2059 Mean?
The PCM has detected an open circuit or malfunction in the reductant injection air pump control circuit. This pump pressurizes the DEF system and without it, the reductant cannot be injected properly into the exhaust stream.
Common Causes
35%
Failed reductant injection air pump motor or internal circuit
25%
Damaged or disconnected wiring to the air pump
20%
Blown fuse or failed relay for air pump circuit
12%
Corroded or loose connector at air pump
8%
Failed DEF control module pump driver circuit
Diagnostic Steps
1
Step 1: Check fuses and relays related to DEF air pump operation
2
Step 2: Inspect air pump electrical connector for corrosion, damage, or loose connection
3
Step 3: Test for power and ground at air pump connector with ignition on
4
Step 4: Command air pump operation with scan tool and listen/feel for pump activation
5
Step 5: Measure pump motor current draw and compare to specifications; replace pump if faulty
Estimated Repair Cost
$300 - $1,500
Parts + labor, varies by vehicle and location
The PCM has detected an open circuit or malfunction in the reductant injection air pump control circuit. This pump pressurizes the DEF system and without it, the reductant cannot be injected properly into the exhaust stream.
The most common cause of P2059 (Reductant Injection Air Pump Control Circuit/Open) is: Failed reductant injection air pump motor or internal circuit
Typical repair costs for P2059 range from $300 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains drivable but DEF injection system will not function. Will cause emissions non-compliance and trigger progressive power reduction or speed limiting after grace period.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2059 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System (SCR/DEF)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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