OBD codes 300, 502, 503, 151

Tiny
ARAINA ROY
  • MEMBER
  • 2003 CADILLAC DEVILLE
  • 4.6L
  • V8
  • TURBO
  • 2WD
  • AUTOMATIC
  • 153,184 MILES
Are these related issues? Does the vehicle speed sensor relate to the o2 sensors? I plan to replace two of the 02 sensors then the two coil packs sets. Are these codes telling me the problem is more or less? Ah, help please.
Do you
have the same problem?
Yes
No
Wednesday, April 3rd, 2019 AT 6:26 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome to 2CarPros.

The P0300 is a random misfire and could be caused by several different things. Yes, the misfire can be related to the heated O2 sensor issue (P0151). However, not to the speed sensor issues.

Now, the o2 sensor code indicates there is too much oxygen in the exhaust. Most times that is related to an engine vacuum leak which can cause a random misfire. With that in mind, I would first check for engine vacuum leaks. Here is a link that shows how it is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you find there are no leaks, then check and confirm that the fuel pump pressure is within the manufacturer's specs. Here is a link that shows how that is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If you look at the attached pictures, they are diagnostic flow charts related to fuel pressure issues in case you find the pressure is not correct. The last pic provides the manufacturer's specs for pressure.

__________________________________________

Lets start with this and let me know what you find. Honestly, to just replace the coils and sensor may not fix the issue.

Let me know what you find.

Take care,
Joe

Was this
answer
helpful?
Yes
No
Thursday, April 4th, 2019 AT 6:46 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello,

There are two separate issues going on here Direct Trouble Codes (DTC)(s) P0300 and DTC P0151 are one issue and DTC P)502 and DTC P0503 are another issue. In the diagrams down below I have included factory description and troubleshooting diagnostic flowcharts for each of the four DTC's for you to go through. It is a lot of information, but please go through each one and keep in mind that there are two separate issues here. Please get back to us with what you find out.

Thanks,
Alex
2CarPros
Was this
answer
helpful?
Yes
No
Thursday, April 4th, 2019 AT 7:41 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

DTC's continued in the diagrams down below.

Thanks,
Alex
2CarPros
Was this
answer
helpful?
Yes
No
Thursday, April 4th, 2019 AT 7:43 PM
Tiny
ARAINA ROY
  • MEMBER
That is a ton of help. I will begin tomorrow because I will have the entire weekend and the coil packs and o2 sensors just arrived. It looks like if I am correct I can get a new VSS for around $20.00. I will start with by checking for vacuum leaks, which is possible, because originally the lines were a hard plastic and given the car is sixteen years old they break easily. When I changed the thermostat recently, a few months ago I broke some and replaced them with newer more pliable lines. My current issues are just a few weeks old so I don't think they are the cause. I will however let you know how things go. Thank you for the quick reply.
Was this
answer
helpful?
Yes
No
Thursday, April 4th, 2019 AT 10:25 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

That sounds like a plan. Let me know what you find or if you have other questions.

Joe
Was this
answer
helpful?
Yes
No
Friday, April 5th, 2019 AT 5:45 PM

Please login or register to post a reply.

Recommended Guides