The “Service Engine Soon” indicator came on, so I started down the path to learn about this truck’s engine management codes and what could be causing them.
I use the VeePeak OBD2 Bluetooth module connected to the OBD2 port with the OBD Fusion IOS app to monitor my newer vehicles. I have been using it in the Discovery as the stock temp gauge is as useful as a dummy light. It shows very little movement unless you are already overheating, so I have been curious how the temp swings on this engine during the very hot weather we have been experiencing lately. The Discovery is able to keep the temperate under control even in 100 degree weather with the AC going and idling at a light. Have seen the temp spike to 202° for a moment, but then a fan must come on as it cools down quickly.
But back to the issue at hand. I have a “Service Engine Soon” light to deal with.
Monitored codes for a few days and found P1174 “system too lean” and P0134 “LH O2 Sensor no activity”
Then a couple more…
….P1174 codes
Things seemed to be pointing to the front left O2 sensor. Made sense to swap the front sensors and see if the problem switched sides.
Upstream O2 sensors
Time to remove and swap them
This tool makes removing them possible
When re-installing its necessary to use some high temp O2 sensor compatible anti-sieze
Used tool to tighten
After the swap had P0154 “RH O2 no activity” and a couple of “system too lean” codes
As well as a “secondary air injection system malfunction” code
Well, the P0154 code followed the O2 sensor, so I decided to change it out.
New OEM Bosch sensor in stock at my local Autozone. These come with anti-seize already applied to the threads
After installing, I was still getting the “system too lean” codes
Time to look for other issues. Next up was looking for vacuum leaks. An obvious place to check was the brake booster vacuum connection to the intake manifold as this had RTV around it from the previous owner. Must have had a leak there before. With the engine idling, I felt around this connection and my hand next to the vaccum leak made the hissing sound loud enough to hear over the engine noise.
Some electrical tape and zip ties to stop it unraveling in the engine heat fixes the immediate problem
Will change out the connector at the manifold and the vacuum hose, but it looks like the intake needs to be removed to push the connector out from inside the manifold. Will look at the forums to see if there is a good way to do this without removing the intake, otherwise it goes on the list as a later project to tackle.
Have been running for a couple of weeks without codes….fingers crossed.
