What Does P1590 Mean?
This code indicates the neutral position switch (also called the neutral safety switch or transmission range sensor) circuit is reading an abnormally high voltage. The PCM uses this switch to determine the gear selector position for starting logic, backup light control, and transmission shift strategy. A high input suggests an open circuit, failed sensor, or wiring fault pulling the signal voltage up.
Common Causes
30%
Failed neutral position switch (internal open circuit)
25%
Open or broken wire in the switch signal circuit
20%
Corroded or disconnected connector at the switch
15%
Misadjusted manual linkage causing incorrect switch contact position
10%
PCM ground or reference voltage circuit issue
Diagnostic Steps
1
Monitor the neutral position switch signal voltage on live data while cycling the gear selector through all positions; look for consistent high readings or dropouts.
2
Locate the neutral position switch on the transmission and inspect the connector for damage, corrosion, or disconnection.
3
Check for continuity through the switch in the appropriate gear positions; the switch should close specific circuits in each detent.
4
Verify the signal wire from the switch to the PCM is intact—check for opens, especially at stress points near the transmission.
5
If the switch is externally mounted, check its adjustment relative to the shift linkage; readjust if needed per service manual procedures.
Estimated Repair Cost
$100 - $350
Parts + labor, varies by vehicle and location
This code indicates the neutral position switch (also called the neutral safety switch or transmission range sensor) circuit is reading an abnormally high voltage. The PCM uses this switch to determine the gear selector position for starting logic, backup light control, and transmission shift strate...
The most common cause of P1590 (Neutral position switch circuit high input) is: Failed neutral position switch (internal open circuit)
Typical repair costs for P1590 range from $100 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A faulty neutral position switch may allow the engine to start in gear or prevent starting altogether. Incorrect gear position data can also cause erratic shift behavior in automatic transmissions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1590 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Starting System
Difficulty
Type
Manufacturer
Recommended Tools
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