The oxygen sensor ahead of the catalytic converter contains a small heater so it can start working before the exhaust warms it up. The car has detected that this heater circuit is not drawing the current it should. Until it is fixed, the engine runs on a preset fuelling map for longer than it should after every cold start.
The oxygen sensor ahead of the catalytic converter contains a small heater so it can start working before the exhaust warms it up. The car has detected that this heater circuit is not drawing the current it should. Until it is fixed, the engine runs on a preset fuelling map for longer than it should after every cold start.
The code is stored by the engine control unit the moment the reading falls outside the range the manufacturer allows. Stored is not the same as diagnosed: P0135 names the symptom the car detected, not the part that caused it. That is why the repair figures below sit in a range rather than at a single price.
In rough order of how often each one turns out to be the culprit:
Parts cost roughly the same wherever you are. What moves the total is the shop rate, which is why the same job is two to three times the price in the United States that it is in Italy. These figures assume an independent workshop, not a franchised dealer, and cover the cheapest and the most expensive of the causes listed above.
| Country | Parts | Labour | Total |
|---|---|---|---|
| United States | $30 to $170 | $50 to $180 | $80 to $350 |
| United Kingdom | £25 to £140 | £30 to £120 | £60 to £260 |
| Germany | €30 to €160 | €40 to €150 | €70 to €310 |
| Italy | €30 to €160 | €20 to €70 | €50 to €230 |
Based on 0.4 to 1.5 hours of book labour at local shop rates, plus parts at local retail. Indicative ranges, not quotes.
Yes. This fault rarely leaves you stranded, but it still has to be fixed before the car will pass an emissions test.
Yes, in every market we cover. The warning light alone fails the emissions check, and an emissions fault that is cleared on the morning of the test comes back as soon as the readiness monitors run again.
Clearing the code the day before a test is a false economy: erasing the memory also resets the readiness monitors, and a car that arrives with its monitors incomplete is refused on that ground alone in most testing regimes.
On its own this is a small item. What makes it worth checking is the company it keeps: a car with this code and nothing else is a car with a minor fault, while the same code next to cleared readiness monitors usually means somebody wiped the memory before you arrived.
The thing worth checking is not the code on its own. It is whether the memory was cleared recently. Every car keeps two numbers alongside the fault list: the distance travelled since the codes were last erased, and the state of the readiness monitors. A car with no stored faults, incomplete monitors and 30 km since the last reset was wiped in the seller's driveway, probably this week. That combination tells you more than any single code does.
TrustThisCar reads all of it during the viewing, in three minutes, with the kind of Bluetooth adapter that costs about 20 euro: stored, pending and permanent codes, readiness monitors, distance since the last reset, and a verdict in plain words you can send to the seller while you are still standing next to the car.
The oxygen sensor ahead of the catalytic converter contains a small heater so it can start working before the exhaust warms it up. The car has detected that this heater circuit is not drawing the current it should. Until it is fixed, the engine runs on a preset fuelling map for longer than it should after every cold start.
Yes. This fault rarely leaves you stranded, but it still has to be fixed before the car will pass an emissions test.
Yes, in every market we cover. The warning light alone fails the emissions check, and an emissions fault that is cleared on the morning of the test comes back as soon as the readiness monitors run again.
It depends on the shop rate where you live: United States $80 to $350, United Kingdom £60 to £260, Germany €70 to €310, Italy €50 to €230. Parts are close to the same everywhere; labour is what moves the total.
Last reviewed 2026-10-03.