P1655 — PSP Switch Out of Self Test Range

OBD2 code P1655 flags a problem with the sensor and actuator circuits (PSP switch out of self test range). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, blown fuse feeding the circuit, control module driver fault.

For Ford vehicles

starter disable circuit

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1655 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the PSP switch out of self test range for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1655 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1655 (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250. Overall, fixing P1655 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What is the most common cause of P1655?

The most common causes are: poor ground connection, blown fuse feeding the circuit, control module driver fault.

Will P1655 clear itself?

Sometimes P1655 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

Is it safe to drive with P1655?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

What are the symptoms of P1655?

Drivers most often notice: increased fuel consumption in some cases, Check Engine Light on, the affected system operates intermittently or not at all, possible limp mode depending on the affected component.

What does OBD2 code P1655 mean?

The engine control module (ECM) logs trouble code P1655 when it finds that the power steering pressure switch or related actuator circuit is operating outside its expected range during the module's self-check routine. This is not a sensor reading that goes bad gradually — the fault is detected the moment the ECM runs its internal diagnostic sequence and sees a signal that falls outside the factory-calibrated window. When that happens, the module flags P1655 and illuminates the Check Engine light.

To understand why this matters, it helps to know what the PSP switch actually does. On most applications, the power steering pressure switch tells the ECM how much load the steering system is under. The module uses that information to adjust idle speed and, on some vehicles, to modulate accessory load. During a normal drive cycle, the ECM performs a self-test on its inputs and outputs. If the PSP switch circuit shows a voltage or resistance that does not match what the calibration expects — whether it is too high, too low, or completely absent — the test fails and P1655 is set. The ECM also captures a freeze frame at that instant, recording engine speed, calculated load, coolant temperature, and vehicle speed. That snapshot is the best place to start the diagnosis because it shows exactly what conditions triggered the fault.

Common symptoms of P1655

The Check Engine light remains on after the fault is detected.
Fuel economy may drop noticeably, especially if the ECM changes its idle or fueling strategy because it cannot read the PSP switch correctly.
The affected system — typically power steering assist or related accessories — may operate inconsistently or stop responding as expected.
On some vehicles the ECM triggers a reduced-power or limp-home mode until the fault clears.
You may notice harder-than-usual steering at idle or low speeds if the module disables its power steering compensation logic.
In rare cases, unrelated symptoms such as stalling or poor throttle response appear because the ECM is operating with incomplete data from the PSP circuit.

What causes P1655?

A blown fuse or failed fusible link that supplies power to the PSP switch or its control circuit.
An internal fault within the ECM itself — specifically a driver circuit that has failed, which means the module cannot properly send or receive the signal.
A connector that is corroded, pushed in partially, or has bent pins — any of which interrupts the electrical path.
A weak or oxidized ground at the switch or at the ECM, causing the signal to drift out of range.
Wiring that is open (broken), shorted to ground, or shorted to another circuit, producing a voltage reading the ECM cannot interpret.
On higher-mileage vehicles, wear and vibration can loosen the harness near the steering rack or pump, making the connection intermittent.

How to diagnose P1655

Hook up an OBD2 scan tool and confirm that P1655 is stored, not just pending. Record the freeze frame data before clearing anything — those engine conditions tell you what to replicate during the drive cycle.
Look for any other trouble codes present at the same time. Secondary codes — especially those pointing to sensors, ground circuits, or communication lines — often point to the real root cause behind P1655 rather than the switch itself.
Check for any manufacturer technical service bulletins (TSB) that apply to this code on your specific make and model. Some vehicles have known software updates or harness revisions that resolve the issue without part replacement.
Inspect the wiring and connectors tied to the PSP switch. Pull the connector apart and look for corrosion, bent pins, or broken wires at the harness exit points. This is where most failures occur on older vehicles.
With a multimeter, verify that the circuit has the correct reference voltage, a solid ground, and proper signal continuity. Wiggle the harness while monitoring the reading — any drop or interruption indicates a broken wire inside the insulation.
Clear the code, then drive the vehicle through the conditions recorded in the freeze frame (same RPM, load, temperature range, and speed). If P1655 returns, the fault is confirmed and the circuit needs further repair.

How to fix P1655

Address the least expensive and most common culprits before replacing major components:

Repair or replace damaged wiring and connectors — this fixes the majority of intermittent PSP switch faults and is the most affordable route.
Replace the faulty sensor or actuator if the switch itself is confirmed defective — most shops charge between $150 and $500 for the part and installation.
Repair or replace the ECM if internal driver circuitry has failed — this is less common but more costly, ranging from $300 to $1,000 depending on whether the module can be reprogrammed or must be replaced outright.

How much does it cost to fix P1655?

The total bill depends on what actually caused the fault. Here are typical parts-and-labor scenarios at independent shop rates in the United States:

Wiring harness repair or connector replacement: $80–$250
PSP switch or related actuator replacement: $150–$500
ECM repair or replacement: $300–$1,000

Most vehicles with P1655 fall toward the lower end of that range. A thorough visual and electrical inspection before purchasing parts is the single best way to avoid an unnecessary $500 repair when the fix was really a loose ground wire.

Can you drive with P1655?

In most cases the vehicle remains drivable after P1655 sets. You may notice slightly reduced performance, harder steering at idle, or an illuminated Check Engine light that will fail an emissions inspection. However, if the fault causes the ECM to fall back into a default strategy that affects braking, steering assistance, or engine response, treat it as urgent and have it diagnosed promptly.