1997 5.7L PU, p0161 p0118 p1115

[Brocktoon]

The last few months, I've been trying to track down a P0118 (Engine coolant temp sensor high voltage) and P1115 (Engine coolant temp sensor circuit intermittent high voltage) on my 97 K1500. I first replaced the ECT sensor up top, which worked for awhile, but developed a bad jerk when accelerating. In October, I replaced the connector, and that took care of the jerking. This morning, the CEL came back on a few minutes after startup, and again it showed the P0118 and P1115, along with P0161 (O2 Sensor heater B2S2). Is the p0161 related in any way to the ECT circuit codes, or am I just chasing my tail again?

Another issue I've been dealing with for awhile:
The truck also has an intermittent hard/weak start after sitting for a few hours or during normal drive cycles (going to stores, work, etc) It does NOT do this after sitting overnight or longer. When starting for the first time in the day, it fires up perfectly. I tested fuel pressure, which seems ok (57 psi, IIRC). Pressure does drop slightly when I pinched off feed and return lines at fuel pump, but not drastically or at a fast rate. I did replace the original spider injector system with the upgraded MPFI system last March, and fuel pump in May 2022. The fact that it'll start right up after sitting for days at a time makes me think it's not fuel related, but I have no idea anymore, I've been wrong in just about everything I've tried to fix on this truck.

 

[Schurkey]

How old are the O2 sensors?

My '97 K2500 had O2 sensor heater codes for all four, and when I discovered that, they were all replaced. 160K + miles, and I think the O2 sensors were originals. Prior owner had...issues.

 

[Brocktoon]

The only one I've replaced since I bought the truck in 2015 is B1S2. I put a Bosch sensor in around 2018, I think. The other three are pre-2015, possibly even original.

 

[Schurkey]

Replace AT LEAST the three older sensors.

I expect the O2 sensor code is not related to the temp sensor codes.

What does "hard/weak start" mean? Engine cranks but won't start? Or cranks slowly/weakly?

 

[Brocktoon]

It's an extended slow/weak crank. It feels like it won't catch, but does, for now. It does seem a little better now that it's cold out than it was over the summer. Heat soaked starter, maybe?

 

[Schurkey]

Verify the battery is fully-charged, the battery terminals are shiny--not fuzzy green, not black--and the cables are similarly clean at each end (positive AND negative.) Assure that the battery voltage does not drop excessively during cranking.

If you correct any issues, re-test. If it's good...it's good. If not, perform voltage drop (VD) testing.

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If the battery, cables, and connections are proven good, replace starter motor.