Another CEL Code 52 Thread 1994 FZJ80.

Joined
Jun 9, 2013
Messages
89
Location
North Carolina
Mudders,

Lend me your ears.

I am currently getting a CEL Code 52 (Knock Sensor No. 1) that will not go away.

Backstory - Friday, pulling out of Central NC and got a CEL. Pulled into an autozone parking lot up the street, jumped the diagnostic connectors and revealed a code 52 (Knock Sensor No. 1). Went to inspect the knock sensor and the wire had broken off from the sensor at the connector. Called the Toyota dealership in VB where I was heading and ordered the appropriate pig tail to splice in when I arrived. Drove the truck in Safe Mode up (Took Country roads, Kept it around 2000 rpm at max) and installed the new pigtail and aftermarket sensor Saturday morning. Drove the truck around Saturday evening with no issue or CEL what so ever.. Sunday evening, CEL came on again.

Here's what I've done.

Replaced Knock Sensor, albeit with an Aftermarket one. Verified that it works via oscilloscope.

Checked continuity along the wire from the sensor to the ECM. Was not able to get an OHM reading down the wire (from sensor cap to appropriate pinned connector in the 16 pin ECM connector, however was able to generate a AC Voltage reading increase at the ECM connector when stimulating the sensor at the block with the wire connected)

Checked spark plugs. All good.
Filled the truck up with High Octane Gas.
Checked Timing. 9-10 BTDC.

Reset codes. No change. Even after it drops the code, the engine timing only retards 3ish degrees to 6-7 BTDC.

Timing is spot on at 9-10 BTDC. No loud knocking. No sputtering. No lurching. No drop in power. When putting the OBD1 ECM into Service mode it drops my timing to 5 BTDC.

Trying to hunt this electrical gremlin down.. I'm assuming its the wire. Only assuming because I have not received any codes for the No. 2 Knock Sensor, performance of the engine does not suffer terribly at current timing, engine temps stay the same, just the CEL light comes on.


HAAAAALLLLLPPPP!!!! I need the cruiser guru's to weigh in on this one, as shy of routing a co-ax from the sensor to the ECM I've done what I've found most mudders doing on the Forum.
 

baldilocks

Battle Ground, WA
GOLD Star
Joined
Jan 29, 2014
Messages
7,343
Location
Battle Ground
Are you saying that the static timing is set at 9-10 deg? Before I replaced any more parts or chased this any further, I would set the time to the factory specified 3 deg before TDC and go from there.

Was the new pigtail spliced in using a crimped connector or was it soldered in? Soldered connections are frowned upon in the FSM but even a crimped connection can be a problem if not done carefully.
 
Joined
Jun 9, 2013
Messages
89
Location
North Carolina
Are you saying that the static timing is set at 9-10 deg? Before I replaced any more parts or chased this any further, I would set the time to the factory specified 3 deg before TDC and go from there.

Was the new pigtail spliced in using a crimped connector or was it soldered in? Soldered connections are frowned upon in the FSM but even a crimped connection can be a problem if not done carefully.
Originally timing when investigated was -3 BTDC.

I advanced the timing seeing as it was retarded 6 below the standard while in service mode ( 3 degrees per the FSM) and we went from there. I adjusted it per this thread…FSM says normal timing when in Neutral without A/C on is 2-13 degrees. Unless I'm reading it wrong. I also followed this thread on advancing the timing outside of spec for performance.


There isn’t/hasn’t been/wasn’t any audible pinging or knocking present. The new pig tail was crimped in.

Upon swinging by the local dealership and talking with their foreman it seems I may be chasing a “shielding gremlin” as the original line is shielded and it’s apparently common for the wire to have interference issues even while still showing continuity at its age. Particularly where it comes in close proximity to the EGR.

Drove the truck yesterday for 4.5 hours without it throwing the CEL at me. Since then it has come on once this morning and gone off and hasn't returned since. 🤦🏻‍♂️🤷🏻‍♂️

Aside, from my timing being advanced the only variable I have found is my Primary Coil Resistance was 0.95 Hot vs. what the manual says it should be (0.45-0.65 ohms). I brought up the coil resistance to the shop foreman and he seemed unconcerned with the deviation in the hot ohms for the Primary Coil as it's still HOT AF in Central NC right now.
 
Last edited:

Users who are viewing this thread

Top Bottom