P1393
FordGlow Plug Circuit Low Input (Bank #2)
The engine computer has detected a low input in the glow plug circuit for Bank #2. Glow plugs warm diesel engine cylinders to help with cold starting. This code identifies a circuit condition; it does not prove that a glow plug itself has failed. Exact applicability depends on the vehicle’s model, year and engine.
⚠️ Before You Begin (Safety First)
This fault may make cold starting unreliable, but it usually does not by itself require stopping immediately. Do not handle glow plug wiring or components while the engine is hot. Glow plug circuits carry substantial current; avoid improvised tests or bypasses. Stop in a safe place if the engine runs severely rough, stalls, or produces heavy smoke.
Common Symptoms
- There may be no noticeable symptoms, especially when the engine is warm.
- Cold starting may take longer if Bank #2 glow plugs are not heating as intended.
- The engine may run rough briefly after a cold start if cold combustion is affected.
- White exhaust smoke may occur during a cold start when combustion is incomplete.
Common Causes
- Damaged, loose or corroded wiring or connections in the Bank #2 glow plug circuit may reduce the monitored input.
- A glow plug fault may affect the circuit reading, but the code does not identify a particular plug as defective.
- A fuse, relay, glow plug control unit or other power-supply fault may prevent the circuit from receiving the expected input.
- A short or other wiring fault may pull the circuit input low.
Diagnostic Steps
- Check the owner’s manual or vehicle information to confirm the engine is equipped with a Bank #2 glow plug circuit; bank layout and applicability vary.
- With the engine off and cool, visually inspect accessible Bank #2 glow plug wiring and connectors for looseness, corrosion, chafing or heat damage.
- Do not unplug or test high-current components unless the vehicle-specific procedure makes the safe method clear; refer electrical measurements to a qualified technician if unsure.
- Record the code and any related codes before clearing anything, then note whether the starting symptoms occur mainly when the engine is cold.
- If the code returns or starting is affected, have the Bank #2 circuit tested against the correct wiring information rather than replacing parts by guesswork.
When to Call a Professional
Confirm that the engine and scan-tool data support a Bank #2 glow plug circuit, then diagnose that bank using the vehicle-specific wiring information. Check the circuit’s power supply, connections, wiring, control components and glow plugs with appropriate electrical tests. A low input can result from more than one fault, so do not replace glow plugs based on this code alone.
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Commonly Asked Questions
Does P1393 prove a Bank #2 glow plug has failed?
No. It reports a low input in the Bank #2 glow plug circuit. Wiring, connections, power supply or control components can also cause that condition.
What does Bank #2 mean?
It identifies the engine bank associated with the monitored circuit. Whether the vehicle has a Bank #2 glow plug circuit depends on its engine and configuration.
Can I keep driving with this code?
The code usually affects cold starting more than normal driving. If the engine starts and runs normally, it is generally not an immediate stop-driving condition, but arrange diagnosis. Stop safely if the engine stalls, runs severely rough or produces heavy smoke.
Should I replace the glow plugs first?
No. Have the Bank #2 circuit checked first. The code alone does not identify a failed plug, and a wiring or power-supply fault can produce a similar low-input condition.
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