What Does P0585 Mean?
The ECM has detected a correlation fault between the cruise control multi-function input 'A' and input 'B' circuits. These two inputs should have a defined relationship, and when the ECM detects that their signals are inconsistent or contradictory, it sets this code. This may indicate one circuit is working while the other has drifted, or both are present but their values do not match the expected paired relationship.
Common Causes
35%
One of the two cruise control input circuits has drifted due to a corroded connector adding resistance to one path but not the other
30%
Partially failed cruise control switch assembly where one resistive-ladder channel has degraded while the other remains in specification
20%
Clock spring with a high-resistance fault on one cruise control trace but not the other, causing the two inputs to diverge
15%
Wiring fault on one input circuit (partial short or open) that shifts voltage readings on that circuit only
Diagnostic Steps
1
Step 1: Monitor both cruise control input 'A' and input 'B' voltages simultaneously on live data. Press each cruise button and compare the readings. They should follow a manufacturer-defined correlation pattern.
2
Step 2: Identify which input is out of specification by comparing each reading to the manufacturer's voltage chart independently. The circuit that deviates from specification is the one with the fault.
3
Step 3: Measure resistance at the switch connector for each input circuit independently. Compare to manufacturer specifications. A significant deviation on one channel points to the faulty circuit.
4
Step 4: Check connector resistance on each circuit path (clock spring, column connector, ECM connector). A few ohms of added resistance on one path can shift the voltage enough to fail the correlation check.
5
Step 5: Clean or replace connectors that show corrosion. If the switch assembly has one degraded channel, replace the entire switch assembly. Verify both inputs correlate correctly across all button positions after repair.
Estimated Repair Cost
$40 - $400
Parts + labor, varies by vehicle and location
The ECM has detected a correlation fault between the cruise control multi-function input 'A' and input 'B' circuits. These two inputs should have a defined relationship, and when the ECM detects that their signals are inconsistent or contradictory, it sets this code. This may indicate one circuit is...
The most common cause of P0585 (Cruise Control Multi-Function Input "A"/"B" Correlation) is: One of the two cruise control input circuits has drifted due to a corroded connector adding resistance to one path but not the other
Typical repair costs for P0585 range from $40 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The ECM disables cruise control when a correlation fault is detected, as it cannot trust the driver's intended input. This is a safety-oriented response that prevents unintended cruise behavior. Normal driving is unaffected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0585 to identify the root cause.
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Quick Info
Category
Powertrain
System
Cruise Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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