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Message: [QUOTE="bismic, post: 1569026, member: 1537"] The link I posted shows your ICP sensor location. It helps to understand the situations where unplugging the ICP sensor actually will make a difference. Unplugging a [I][U]good[/U][/I] ICP sensor that has no wiring issues will not help a no-start. It certainly is an easy enough thing to try though, and especially because we just don't quite get enough information from the PCM on whether or not the IPR valve is actually functioning properly! Unplugging the ICP sensor when there is insufficient high pressure oil pressure for a start (leak or bad HPOP) will not enable the engine to start either. Also, there are a lot of things that cause a no-start that are unrelated to the high pressure oil system. If/when you do unplug the ICP sensor, you should also inspect the connector for oil soaking (leaking sensor) and for wire chafing. The thing about the ICP and IPR is that the software (PCM) can account for some errors in the ICP sensor - by design. That said, many times issues happen when there are problems with BOTH the ICP accuracy, AND when the IPR valve is [I][U]ALSO[/U][/I] sticking or "acting up". This is why it really helps to look at ICP sensor voltage at KOEO. It should be around .2v (some small difference in model year sensors). Then we look at cranking ICP sensor voltage AND we also need to look at the IPR commanded Duty Cycle %. What complicates things is that the IPR % Duty Cycle is a command, not an actual value. When troubleshooting, we need to be aware that there is both a software minimum to start (500 psi), and a slightly lower "actual value" for adequate pressure for the injectors to actuate properly to enable a start (assuming a healthy fuel injection system and proper compression, etc). Again, for this reason we look for the health of the sensor (watching sensor voltage output) and watch the IPR valve commanded position. So if the ICP sensor is reading higher than the actual pressure (bad sensor), it can reach the desired ICP sensor voltage output value before it should (ie exceeding the software/PCM minimum before it should) - this can happen with or without a sticking IPR valve. If only the ICP sensor is bad, the PCM is programmed to hopefully "catch it" and to assume a value (a value high enough to enable a start). In some cases the PCM doesn't do this, and this is when unplugging the sensor helps (unplugging it forces the PCM to assume a value). A sticking IPR valve can cause the actual pressure value to be below the minimum pressure required to start (PCM and mechanical minimums). So this failure will significantly complicate the troubleshooting when you ALSO have a bad sensor. This situation happens when a bad ICP sensor shows good pressure at an IPR commanded duty cycle that the PCM "thinks" is appropriate (but in this described situation, the actual position of the valve is not matching the commanded value). Summary: unplugging a bad ICP sensor most likely isn't going to enable a start when the IPR valve is [I][U]ALSO[/U][/I] stuck too far open (or as stated above, if there is a bad leak or if the HPOP is bad). [U]To REALLY understand what is going on (as best as we can anyway), you need to monitor the following cranking information:[/U] cranking speed, rpm. ICP sensor volts (KOEO and cranking). ICP desired pressure (cranking). ICP pressure (cranking). Commanded IPR % Duty Cycle (cranking). FICM Sync (cranking). Cam Crank Sync (cranking). Injector Pulse Width command (cranking). (also good to know what KOEO and cranking battery voltage is also - FICM LPower and also VPower will show that ..... knowing both of these voltages is important). Lastly, like most v-reference sensors (5v), if there is a v-reference short within the ICP sensor that interferes with this system voltage, unplugging it can sometimes enable starting (y-ref sensors: ICP sensor, EBP sensor, EGR valve position, MAP, Baro, etc). [/QUOTE]