P1600Manufacturer-specific code

P1600 Code: Engine Computer Backup Power Supply (Toyota, BATT)

On Toyota and Lexus vehicles, the P1600 code means there was a fault in the backup power supply (BATT) of the engine computer. The computer loses what it has learned every time the engine is shut off. Other brands may define this number differently.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$0 to $80
Difficulty
Easy
System
Computer and Outputs
Applies to
Depends on the manufacturer

Common in: Toyota

Updated Reviewed by Renzo Chacca

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What the P1600 code means

P1600 is a manufacturer-specific code: the 1 in the second position means each automaker defines what it means, not the generic SAE standard. The most widespread definition is the one used by Toyota and Lexus. If your vehicle is another brand, confirm the code text with a scan tool that supports that manufacturer.

ManufacturerMeaning of P1600
Toyota and LexusFault in the computer backup power supply (BATT)

The computer gets constant power from the battery (BATT) so it can keep its learned values and codes with the engine off.

It sets the P1600 code when that constant power was interrupted: after the battery was disconnected, or because of a fuse or a wire with a bad contact.

Before you start repairs, confirm the make, model, year and engine. With manufacturer codes, the same number can change even between engines from the same brand.

P1600 code symptoms

  • Check engine light on.
  • Unsteady idle after starting, because the learned values are lost.
  • Readiness monitors go back to not ready.

Likely causes of the P1600 code

  1. Battery recently disconnected. Confirm it with the tests in the diagnosis section.
  2. EFI or ECU-B fuse blown or loose.
  3. Loose or sulfated terminals. Confirm it with the tests in the diagnosis section.
  4. Power wire. Look for rubbing against the engine, the chassis or the exhaust.

How to diagnose the P1600 code step by step

  1. Find out whether the battery was disconnected recently.
  2. Measure 12 V at the BATT pin with the key off.
  3. Check the fuses and terminals.

How to fix the P1600 code

  • Repair the fuse, terminals or wiring.
  • Clear the code.
  • If it was only a battery disconnect, the code should not return.

Technical reference data

  • BATT: 12 V constant with the key off.
  • P1xxx codes are manufacturer-specific: confirm the definition with a scan tool that supports your brand.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

If you just replaced or disconnected the battery, this code is expected. Clear it and see whether it comes back before you go looking for a fault.

P1600 on Toyota

It often appears after a battery change on older Toyota vehicles.

If your vehicle is another brand, check the table above for the meaning its manufacturer gives this code and confirm it with a compatible scan tool.

Frequently asked questions about P1600

What does the P1600 code mean on a Toyota?
It means there was a fault in the backup power supply (BATT) of the computer. The computer loses what it has learned every time the engine is shut off.
Does P1600 mean the same thing on every brand?
No. It is a manufacturer-specific code, so on other brands it may not exist or may mean something different. Confirm it with a scan tool that supports your make.
Can I drive with a P1600 code?
Yes. A P1600 code does not stop the vehicle from running. The idle may be unsteady for a while as the computer relearns.
How much does it cost to fix P1600?
Roughly $0 to $80 on a Toyota. If it was just a battery disconnect, there is nothing to repair, and a fuse or terminal costs very little.
Will a P1600 code clear itself?
It should not return after you clear it, if the cause was only a battery disconnect. If it keeps coming back, check the fuses, terminals and wiring.
What is the most common cause of P1600?
A battery that was recently disconnected. A blown EFI or ECU-B fuse and loose terminals are the next things to check.

Related codes

Questions about the P1600 code

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