After seafoam, problems happen

P0607 is a general OBD2 diagnostic code, meaning it has the same meaning for the Toyota Prius as it would any other vehicle. Basically your engine computer can't do its job to optimise engine efficiency and it's going to keep getting worse.

When you straight pipe your car after a cat theft you basically set yourself up to continue lose more and more money from that theft over time.

Without the essential data from 02 sensors the car is unable to accurately adjust engine settings for the most efficient engine performance and just defaults out which leads to increasingly loss in MPG and overall power over time.

Then ultimately, your engine will develop another problem and you'll be blissfully unaware of that problem because your check engine light has been on since you straight-piped it. So you'll have almost no way of knowing your engine is about to die until it does and the cost of repair will be much higher rather than an easy affordable fix had you not straight piped.

And these days you can buy an aftermarket direct fit cat in $60 range, which is about the cost of materials dumb people spend on straight pipes.

And worst of all, 7 million people a year on earth suffer an untimely death from air pollution ( source ) and the entire planet is also over-heating and catching on fire because we think none of that is our fault and think we have zero obligation to even protect our children, famly, friends and neighbors from deadly air pollution.

So please, next time you hang out with your straight pipe friend and notice some elderly folks that live near him, make sure to remind him that if those people turn up dead, his straight pipe may of been what killed them. As in an elderly person with existing health issues can be pushed over the edge into an untimely demise with the amount of air pollution that's unlawfully not being cleaned through a catalytic converter.

 

" issue with the engine control module (ECM)."

 

Most likely is it changed overall performance of the engine enough to make the default no 02 sensor data setting no longer as efficient. Alternatively it created foam that clogged up some of the engine ventilation passages. That's assuming that they only ran the seafoam briefly, rather than forgetting to change the oil soon after.

 

Find a prius owner who had their Prius cat stolen and ask if they felt power loss when accelerating from a full stop. The engine roars but just slowly catching up to speed.

 

Well, maybe someone will have to diagnose the problem.

First thing I would do is use a scantool and look at engine data in the ECM. What are short and long term fuel trims when driving? How well does the air-fuel sensor work? Any other codes in other ecu's? What condition is the HV battery?

Posted via the PriusChat mobile app.

 

Only the first O2 sensor before the catalytic converter really affects fuel consumption. First O2 sensor creates the close loop with MAF and fuel injector to adjust the fuel+air ratio. You can remove the 2nd catalytic converter that is usually stolen with a straight pipe as long as the catalytic converter that is integrated into the exhaust manifold is still there without creating a trouble code for the catalytic converter. The engine code you have is caused by Seafoam which causes a very rich mixture. Bad catalytic converter is P0420 that tell the main catalytic converter on the exhaust manifold is no longer efficient.

 

One of the worst mistakes in trouble diagnosis is making a correlation without causation and running with it to the extent you dismiss the normal and real issues. Also known as the questionable cause logical fallacy in which two events occurring together are assumed to have established a cause and effect relationship.

Seafoam had nothing to do with it. You should be able to see that based on your admittedly small sample size. Seafoam accomplishes nothing on an engine that runs the proper oil with adequate oil changes. Leaving it in the oil or using too much can be harmful to the longterm wear of rings and bearings. Don't be fooled by the claims for aftermarket additives, they have had no legitimate purpose for decades since carburetors went away and all gasoline started using detergent additives to clean fuel injectors. You never hear about failing injectors that need to be cleaned in port injection engines.

Carbon buildup due to oil consumption and bad egr and pcv design won't be touched by Seafoam in the crankcase and is totally ineffective in the fuel.

Gen3 oil consumption, liquids in the intake manifold, clogged egrs and slow seeping head gasket leaks are issues to address. But not with aftermarket additives.

 

All the mechanics that I've talked to over the years have told me fuel+air ratio is dependent on both the upstream and downstream sensor. Sounds like you're saying that downstream sensor is only verifying if cat worked or not and is not related to fuel+air ratio? Do you have some links of where I can learn more about this to verify it, because I've not heard that before?

 

I may be wrong but from what I understand, the 2nd O2 sensor is only to verify the catalytic converter works well. https://www.aa1car.com/library/o2sensor.htm I believe it is how it works from the wiring diagram in Prius too. Once it is in a close loop, only the 1st O2 sensor is the rich/lean sensor to give feedback to MAF+injectors. When the engine just starts in an open loop, the 2nd O2 sensor may contribute to lean/rich mixtures for getting the catalytic converter to reach operating temperature fast enough.
Starting in 2008, the ECU periodically commands MAF and injector to make the rich and lean mixtures and check if the downstream O2 sensor after the catalytic converter detects it, not just the upstream O2 sensor. This way, we cannot cheat the downstream O2 sensor anymore with the spacer when the catalytic converter is removed.
However, Prius and most cars only monitor the exhaust manifold catalytic converter. The secondary catalytic converter that is often stolen is usually not monitored.
I have never been a fan of any fuel additive especially engine flush products that cause way more harm than good on a good running engine. If the engine starts burning oil, reduce the oil change interval to 5000 miles/6 months, often it helps slowly dissolve the carbon deposit on the piston rings. Use an endoscopy camera to verify the cylinder wall is not badly scored (no more criss-cross pattern).