Electronic Throttle Control Supply Voltage Too Low (Ford)
What does P1658 mean?
The P1658 code means the vehicle's onboard diagnostic system has detected: Electronic Throttle Control Supply Voltage Too Low (Ford). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Reduced engine power warning
- Rough idle
- Intermittent stalling
- Poor acceleration
Probable Causes (Ranked by Likelihood)
- Low battery voltage or weak alternator Very High
- Corroded ground connection at throttle body High
- Damaged wiring in throttle control circuit Moderate
- Failing PCM power supply circuit Low
Step-by-Step Diagnostic Procedure
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Check battery voltage with engine off (should be 12.4V+) and running (should be 13.5-14.5V).
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Inspect throttle body ground wire and connector for corrosion or looseness.
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Measure voltage at the throttle body supply pin with ignition on; compare to specification (typically 5V reference).
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Check for voltage drops on the ground circuit from throttle body to PCM.
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If supply voltage is correct at the PCM but low at the throttle body, repair the wiring harness.
Frequently Asked Questions
Could a weak battery cause P1658?
Yes. Low system voltage directly affects the throttle control system. Test your battery and alternator output first before replacing throttle components.
Is P1658 dangerous?
It can be. Low voltage to the throttle control may cause unexpected power loss while driving. Have it diagnosed promptly.
Can I reset the code and see if it comes back?
You can clear it, but if the underlying voltage issue persists, the code will return. Address the root cause first.