Need some help tackling a rear ABS wheel speed wiring harness replacement.

I've no intention of cutting anything... But Toyota's advice often tends to be bias towards corporate profits and they aren't in any way unbiased experts... I've done 5 minute repairs with battery packs thanks to PriusChat and if you took that same problem to Toyota they'd tell you the whole pack and other components need to be replaced for $5K because those lies are entirely embedded into their culture of making as much money off of repairs as possible and caring about saving the customer money isn't a priority for them.

 

I either read it somewhere or an instructor told me. And it's just common sense from a tech standpoint. It's hard to get to a factory quality level in the field when it comes to modifying wiring, and it's a mission critical system. There's few if any solder connections and crimps need to be absolutely water tight, especially exterior.

I think it was a V6 Camry, there's a EFI ground wire on the back of the intake, doing an intake gasket or something like that the bolt for the wire on the manifold is very hard to access. Going back together I put it on a easier to access bolt about 6 inches away from the original. Same size bolt on the same aluminum part of the manifold. It was a comeback, it threw a ECU code and had to call Toyota Techline and they had seen it happen before.

 

Yes, I'm in the middle of 2 DIY hybrid battery reconditions .
Agree about the profit bias, although it's more so the dealers and the techs that are greedy. At one point corporate told the dealers, hey we can make vehicles with near zero maintenance, the dealers came back, please don't we make money from maintenance. Toyota cares about their reliability, quality, and will they be able to reliably warranty a repair. It's also a lawyer / insurance thing. Replace a harness with a factory harness, that's Toyota factory level. Splice a harness, now you are talking Chrysler.

 

Toyota provides extensive instructions on how to splice their wiring harnesses. The online Electrical Wiring Diagram lets you pull up the Toyota part numbers of repair terminals and the correct parallel crimp sleeve to use with each one.

The only admonitions I've seen against splicing in any Prius repair manual published by Toyota have been those for the bright yellow airbag-system wiring and for the orange high-voltage wiring.

The technology of the wheel speed sensors changed between gen 2 and gen 3.

Gen 2 sensors produce sine waves whose frequency and amplitude correspond to the wheel speed, so the signals get more faint at lower speeds.

Gen 3 sensors produce square pulses whose frequency corresponds to the wheel speed but whose amplitude stays constant. The signals don't grow faint at low speeds.

It's possible there could have been more potential issues with splice quality for the old type of sensor. (Though even the gen 2 manuals, IIRC, did not make any special notes about splicing them.)

The signal-check mode was definitely provided for every technician to use after every job involving a bearing or speed sensor. Skipping that step can result in a comeback, even if nobody spliced anything.

It seems like Toyota decided that having a performance standard for the circuit, and a built-in confirmation test to make sure your work meets it, would be a more practical way of preventing comebacks than just loading you with dos and don'ts.

 

It's aftermarket undercoating. The gen3s have nothing protecting the bottom panels or cables other than weatherproof connectors and rubber grommets where cables go inside the cabin. Once in the cabin the connectors are simpler.

This part of the circuit is a simple 2 wire non-shielded cable. Since yours is aftermarket encapsulated, splicing to the remaining portion makes good sense. A decent splice will not impact the signal. You can prove it with the simplest crimp butt connectors (use the heat shrink type) or my choice, a soldered joint with heat shrink cover. Others routinely do a splice and it works fine.

 

Flex seal/paste

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You will have to remove half of the hard plastic interior panels in the hatch to access the connector which was shown above. Similar to the prep needed to remove the hybrid battery.

Trim 4 does not come with factory undercoating.

Splicing using a piece of a $25 replacement wheel sensor harness is the smart move.

 

If you're going to splice on the exterior do it right, the wheel well gets blasted with road spray. Use a heat shrink (epoxy lined) butt connector. Use the correct crimper that does not cut through the heat shrink insulation. You want the connection to be water proof.

Don't know about the 3rd gen. The CT200H connector was accessible with just the floor items removed, you can reach under the side panels.

 

He's in Minnesota, if that splice isn't waterproof it's not going to last.

Japanese metallurgy on their copper wires has made their wire considerable thinner while retaining capacity. There's almost no factory solder connections anymore, I think it's because the thin wires are adverse to heating. The last place they soldered was splices, now it's all crimp.