Faulty starter relay or starter relay circuit wiring.; Open or shorted wire in the starter signal circuit between the ignition switch and ECM.; Defective ignition switch or starter contacts inside the switch.; Poor connection at the ECM connector or corroded ground points.; Failed park/neutral position switch or clutch start switch on automatic or manual models.; Aftermarket alarm or remote start system interfering with the starter signal wire.; Internal ECM fault, though this is rare compared to wiring and switch issues.

DTC codes / Toyota codes / P1500

P1500 · ToyotaStarter Signal Circuit

Q: What does code P1500 mean?

Starter Signal Circuit. P1500 on Toyota vehicles means the engine control module (ECM) is not receiving a valid starter signal when the ignition key is turned to the START position. The ECM expects a voltage pulse from the starter circuit to confirm the engine is cranking, and it sets this code when that signal is missing, intermittent, or implausible.

P1500 on Toyota vehicles means the engine control module (ECM) is not receiving a valid starter signal when the ignition key is turned to the START position. The ECM expects a voltage pulse from the starter circuit to confirm the engine is cranking, and it sets this code when that signal is missing, intermittent, or implausible.

SystemPowertrain

Code typeToyota specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

The engine may crank normally but the check engine light stays on.
Intermittent no-crank condition where the starter does not engage at all.
The engine may start but the ECM logs the code because the starter signal was not seen during cranking.
Rough idle or stalling immediately after start-up in some cases.
Often no symptoms besides the warning light, especially if the starter still works.

Common causes, most likely first

Faulty starter relay or starter relay circuit wiring.
Open or shorted wire in the starter signal circuit between the ignition switch and ECM.
Defective ignition switch or starter contacts inside the switch.
Poor connection at the ECM connector or corroded ground points.
Failed park/neutral position switch or clutch start switch on automatic or manual models.
Aftermarket alarm or remote start system interfering with the starter signal wire.
Internal ECM fault, though this is rare compared to wiring and switch issues.

How to diagnose and fix it

Verify the battery is fully charged and the starter cranks the engine normally before diagnosing the signal circuit.
Check for stored codes in other modules and inspect the starter relay and fuse for corrosion or failure.
Measure voltage at the ECM starter signal pin while an assistant turns the key to START, looking for the expected pulse.
Inspect the wiring harness from the ignition switch to the ECM for chafing, breaks, or loose connectors.
Test the park/neutral position switch or clutch start switch for continuity in the start position.
If an aftermarket alarm or remote start is installed, temporarily disconnect it and retest the starter signal.
Clear the code and perform a road test with multiple start cycles to confirm the repair.

Starter signal faults that fool good technicians

A common misdiagnosis is replacing the starter motor when the real problem is a missing signal to the ECM, so always verify the ECM sees a crank request before condemning the starter.
Aftermarket remote start or alarm systems spliced into the starter wire are a frequent hidden cause on older Toyota models and can set P1500 without any factory component being faulty.
The park/neutral position switch on automatic Toyotas can wear internally and fail to send the starter signal only in certain gear positions, so test it through the full shifter range.
Corroded ground points on the engine block or chassis can cause a voltage drop that prevents the ECM from recognising the starter signal even when the starter spins.
P1500 can be stored as a pending code after a single failed start attempt, so check freeze-frame data and clear it only after confirming the circuit is sound.

Can I keep driving with P1500?

The vehicle is usually safe to drive if the engine starts reliably, but avoid repeated cranking if the starter does not engage because you may damage the starter or drain the battery. Have the circuit inspected soon, especially if the no-crank condition becomes frequent.

Tools that help

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Guidance is general and written for Toyota vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.