U0100 code

Hello: I recently replaced the headgasket, timing chain, etc. on my v. That seems to be the simple part. The engine will not start (starter does not even engage) and I have a U0100 code. I have checked all the connectors (even took them off and cleaned them with brake cleaner), batteries are in good order, and I am at a loss. Any suggestions will be welcome.

 

Hello I picked up a 2012 Prius v wagon for a swan's song because it had a blown headgasket. I bought it to give to my granddaughter but now beginning to doubt my own wisdom. I have never worked on a hybrid before so the stuff beyond the IC engine is new to me. Had the head resurfaced, valves ground and new headgasket, chain, etc. In so doing I pulled the wiring harness off to the right side of the engine (viewed from front) and tied it out of the way with a strap. After reconnecting everything (at least that is what I thought) I was anxious to drive it out of my shop. However, not! Engine would not even turn over. I got U0100 code and message (My reader does not provide the secondary bits, 211, 212, or 530). I have gone over every connector, cleaned them with brake cleaner, etc. to no affect. I even popped the two large connectors off the ECM and cleaned them. No corrosion - clean as a whistle. Batteries are charged. I have ordered a cable so I can put Techstream on my notebook so I don't at this time know which of those 3 secondary codes might come up. However, in the meantime can you all give me some advice on where or how to chase down each of those codes?

I assume the ECM in this DTC code message is the "computer" on the right fender well with the two connectors I described above. However, where is the PCM? Please don't tell me it is behind the glove box. And, how does this CAN work. Are there copper wires, fibre glass, or what between the various ECM units?

Additionally, I saw a website that described how to reset the ECU. He said to disconnect the HV and LV batteries, unplug the heavy power cord in the fuse box, wait a few minutes, reconnect the HV and LV batteries, replug the power in the fuse box, press the start button on and off 3 times. Does this really work or does the car simply burst into flames? OK, its been a long day. Thanks for your reply. Jim

 

Hello - continuation to my prior message--
I made several measurements at the ODB connector. Here is what I found (R means resistance in ohms and V means volts DC):
Bat neg disconnected
R(chassis gnd, signal gnd) = 0
R(CAN gnd) = open - infinite resistance
R(CAN lo, gnd) = open
R(CAN lo, CAN hi) = 61
R(CAN bat) = open
R(CAN lo, bat) = open

Bat neg connected
V(bat, gnd) = 12.31 - special case, power down console. Following cases with console powered up
V(bat, gnd) = 11.86
V(CAN gnd) = 2.46
V(CAN lo, gnd) = 2.17 their sum is 4.63 rather than 5v as expected

It appears that the CAN is powered via a relay since the resistance measurements show it to be totally disconnected from the battery when the battery is disconnected. However, it must be connected when the power is applied since there is measurable voltage, albeit slightly low.

I downloaded a copy of Techstream and tried to apply it. It could not communicate with the network so it is somewhat useless at present. When I ordered it to test the network it went into a never ending attempt to find the network. However it seems the network is active based on the two voltage measurements, it is not grounded, and there are no breaks in the lines since the terminating resistors were both found (61 ohms).

One final bit: When we got the engine back together, my grandson started it. It ran for about 5 seconds until I screamed at him to kill the engine because it made a loud rattle. I thought I failed to get one of the valve stem caps on or a rocker fell off. I folded the wires back again so I could pull the cam cover. Nothing out of the ordinary was found so I have concluded that the oil drained out of the tappets and had not refilled before we killed the engine. After putting the cam cover back and reattaching the various sensors, etc. we have had this dead system problem.

Hope someone can provide some suggestions or even an answer. Thanks

 

Here are TechStream details: Version 12.20.024.1 Installed on Del notebook using an Oracle virtual computer running xp. The program loads and runs as I would expect. I purchased a Mini-VCI J2534 Standard DBII communication interface cable.

When the program starts I sometimes have trouble getting it to connect to the car. I recall having to start the program then plug in the usb cable to my computer to get it to recognize the connection. One of the TS options is to check the CAN. If I select that option the program goes into a never ending attempt to connect to the CAN.

One of the ToyotaNation posts suggested that a faulty O2 sensor could cause a U0100 error. Not sure how that happens but I will check the sensor. It is one of the many sensors I had to disconnect and reconnect to do the headgasket project.

What I can't get my head around is all the test I made on the CAN seem to be spot-on. The terminating resistors are in place (resistance between Clo and Chi = 60 ohms), rms voltage on Chi and Clo are 2.46 and 2.16vdc respectively. This seems a little low since they don't add to 5v. I put my scope on Clo and Chi at the OBDII connector and there is certainly activity on the network. I just cannot tell which of the bursts are from which "computer".

What I think but have no way of confirming it is that when we started the engine and it ran for a few moments, some sensor detected a problem and shut the ecm down. As I wrote before, then engine started and ran for a few seconds before we killed it due to the loud clattering. Maybe the knock sensor thought it was a pre ignition issue and sent a message to the ECM. I have read that the EGR can make a loud rattle - maybe that was a signal to shut the ECM down. It seems there should be some way to do a cntl-alt-delete for that computer but I haven't found anything describing how to reboot the ecm. I just feel it has something to do with the ecm being "dead" since everything worked perfectly before doing the headgasket job.

I have a complete circuit diagram for the car and have checked the B+ going to the ECM -- 12.6v. I have not checked the ECM output voltage going to the 5v powered sensors. Will check that tomorrow. I need to check to see which sensors use that source. I suppose if it is missing that even more confirms that the ECM is seriously asleep.

Jim