FAQ
TL;DR: Focus 2.0 TDCi P1335 often points to the EGR position sensor; expect about 1.0 V at rest—"Faulty position sensor of the exhaust gas recirculation valve." Test pins 4/6 with a scope and command movement via a scan tool. [Elektroda, moto-kord, post #17151502]
Why it matters: This FAQ helps Ford Focus Mk2 2.0 TDCi owners and techs quickly diagnose and resolve stubborn P1335 faults without guesswork.
Quick Facts
- Expected EGR position sensor signal is near 1.0 V at rest; check control on pin 4 and position on terminal 6 with an oscilloscope. [Elektroda, moto-kord, post #17151502]
- Typical EGR potentiometer sweep: approx. 0.90–1.0 V (closed) up to about 4.5 V (open). [Elektroda, seat21, post #17151388]
- Observed values in-thread: 0.8–1.15 V KOEO; 2.5–2.9 V at idle. [Elektroda, autoas, post #17151431]
- Unplugging the EGR resulted in P0406 (EGR circuit high). [Elektroda, autoas, post #17151149]
- Final fix reported: replacing the engine controller (ECU) cleared P1335. [Elektroda, autoas, post #18277015]
What does code P1335 mean on a Ford Focus 2.0 TDCi?
P1335 here points to an EGR position sensor fault with idle symptoms. Guidance: check pin 4 control, pin 6 position, and expect about 1.0 V at rest. If commanded movement shows no sensor change, replace and initialize the EGR. "Faulty position sensor of the exhaust gas recirculation valve." [Elektroda, moto-kord, post #17151502]
Why does P1335 return after every key cycle?
In this case, the fault reappeared immediately after turning the ignition off and on again. Clearing the code with the engine running held only until the next restart. This pattern indicates the condition is detected at key-on. [Elektroda, autoas, post #17151149]
What voltage should I see on the EGR potentiometer?
Expect approximately 0.90–1.0 V closed and up to around 4.5 V fully open. "EGR potentiometer give voltage readings should be from 0.90–1 V to 4.5 V." Use live data or a multimeter for a quick check. [Elektroda, seat21, post #17151388]
How do I test the EGR control and position signals with a scope?
Use this quick 3-step check:
- Turn ignition on; back-probe pin 4 (control) and pin 6 (position).
- Expect about 1.0 V at rest on the position signal.
- Command EGR movement with a diagnostic tool; if the position value does not change, replace and initialize EGR. [Elektroda, moto-kord, post #17151502]
Is the EGR vacuum-controlled or electric on this engine?
On the reported Focus 2.0 TDCi, the EGR valve is fully electric. No vacuum actuator controlled the EGR in that case. [Elektroda, autoas, post #17151537]
Could a throttle position sensor (TPS) be the cause here?
The car discussed had no throttle plate; only vacuum flaps were present. That makes a TPS fault unlikely in that specific case. Always verify your vehicle’s hardware before testing. [Elektroda, autoas, post #17151314]
What happens if I unplug the EGR to troubleshoot?
Unplugging the EGR produced code P0406 (EGR circuit high). That confirms the ECU detects an EGR electrical fault when disconnected. It does not diagnose the original P1335 root cause. [Elektroda, autoas, post #17151149]
Why does the EGR stop moving once the fault sets?
The author noted that once the error sets at ignition-on, the ECU immobilizes the EGR until you clear the code. After clearing on a running engine, it worked until the next key cycle. [Elektroda, autoas, post #17151431]
Can the crankshaft position sensor trigger P1335?
One workshop description mapped P1335 to a Crankshaft Position Sensor 1 circuit/open. It advised checking the Hall/MRE sensor on the crankshaft as an alternate path. [Elektroda, moto-kord, post #17151435]
Does a DPF delete or tune affect P1335 troubleshooting?
With the DPF already removed in this case, one suggestion was to reload original software and re-adapt, or switch EGR off in software as configured. Software state can influence EGR strategies. [Elektroda, seat21, post #17151827]
What live values were seen on this Focus?
Reported readings: about 0.8–1.15 V with ignition on, and about 2.5–2.9 V at idle. Those sit within a typical 0.90–4.5 V sweep, yet the code persisted. [Elektroda, autoas, post #17151431]
What ultimately fixed the P1335 in the thread?
Replacing the engine controller (ECU) resolved the problem in the reported case. After ECU replacement, the P1335 fault did not return. [Elektroda, autoas, post #18277015]
My car runs fine—can P1335 still appear?
Yes. The author stated the car started and drove well despite the warning light. The fault arose after glow plug replacement and with a previously removed DPF. [Elektroda, autoas, post #17151455]
Why do Autocom and FORScan describe P1335 differently?
Autocom labeled it “EGR temperature sensor—present.” FORScan showed “P1335-62—operation of the EGR system with the throttle position sensor in the idle position.” Text differs, but both reference the EGR system. [Elektroda, autoas, post #17151149]
